Semiconductor chip assembly with post/base heat spreader and signal post

ABSTRACT

A semiconductor chip assembly includes a semiconductor device, a heat spreader, a conductive trace and an adhesive. The semiconductor device is electrically connected to the conductive trace and thermally connected to the heat spreader. The heat spreader includes a thermal post and a base. The thermal post extends upwardly from the base into a first opening in the adhesive, and the base extends laterally from the thermal post. The conductive trace includes a pad, a terminal and a signal post. The signal post extends upwardly from the terminal into a second opening in the adhesive.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.12/616,773 filed Nov. 11, 2009, which is incorporated by reference. Thisapplication is also a continuation-in-part of U.S. application Ser. No.12/616,775 filed Nov. 11, 2009, which is incorporated by reference. Thisapplication also claims the benefit of U.S. Provisional Application Ser.No. 61/257,830 filed Nov. 3, 2009, which is incorporated by reference.

U.S. application Ser. No. 12/616,773 filed Nov. 11, 2009 and U.S.application Ser. No. 12/616,775 filed Nov. 11, 2009 are each acontinuation-in-part of U.S. application Ser. No. 12/557,540 filed Sep.11, 2009 and a continuation-in-part of U.S. application Ser. No.12/557,541 filed Sep. 11, 2009.

U.S. application Ser. No. 12/557,540 filed Sep. 11, 2009 and U.S.application Ser. No. 12/557,541 filed Sep. 11, 2009 are each acontinuation-in-part of U.S. application Ser. No. 12/406,510 filed Mar.18, 2009, which claims the benefit of U.S. Provisional Application Ser.No. 61/071,589 filed May 7, 2008, U.S. Provisional Application Ser. No.61/071,588 filed May 7, 2008, U.S. Provisional Application Ser. No.61/071,072 filed Apr. 11, 2008, and U.S. Provisional Application Ser.No. 61/064,748 filed Mar. 25, 2008, each of which is incorporated byreference. U.S. application Ser. No. 12/557,540 filed Sep. 11, 2009 andU.S. application Ser. No. 12/557,541 filed Sep. 11, 2009 also claim thebenefit of U.S. Provisional Application Ser. No. 61/150,980 filed Feb.9, 2009, which is incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to semiconductor chip assembly, and moreparticularly to a semiconductor chip assembly with a semiconductordevice, a conductive trace, an adhesive and a heat spreader and itsmethod of manufacture.

2. Description of the Related Art

Semiconductor devices such as packaged and unpackaged semiconductorchips have high voltage, high frequency and high performanceapplications that require substantial power to perform the specifiedfunctions. As the power increases, the semiconductor device generatesmore heat. Furthermore, the heat build-up is aggravated by higherpacking density and smaller profile sizes which reduce the surface areato dissipate the heat.

Semiconductor devices are susceptible to performance degradation as wellas short life span and immediate failure at high operating temperatures.The heat not only degrades the chip, but also imposes thermal stress onthe chip and surrounding elements due to thermal expansion mismatch. Asa result, the heat must be dissipated rapidly and efficiently from thechip to ensure effective and reliable operation. A high thermalconductivity path typically requires heat conduction and heat spreadingto a much larger surface area than the chip or a die pad it is mountedon.

Light emitting diodes (LEDs) have recently become popular alternativesto incandescent, fluorescent and halogen light sources. LEDs provideenergy efficient, cost effective, long term lighting for medical,military, signage, signal, aircraft, maritime, automotive, portable,commercial and residential applications. For instance, LEDs providelight sources for lamps, flashlights, headlights, flood lights, trafficlights and displays.

LEDs include high power chips that generate high light output andconsiderable heat. Unfortunately, LEDs exhibit color shifts and lowlight output as well as short lifetimes and immediate failure at highoperating temperatures. Furthermore, LED light output and reliabilityare constrained by heat dissipation limits. LEDs underscore the criticalneed for providing high power chips with adequate heat dissipation.

LED packages usually include an LED chip, a submount, electricalcontacts and a thermal contact. The submount is thermally connected toand mechanically supports the LED chip. The electrical contacts areelectrically connected to the anode and cathode of the LED chip. Thethermal contact is thermally connected to the LED chip by the submountbut requires adequate heat dissipation by the underlying carrier toprevent the LED chip from overheating.

Packages and thermal boards for high power chips have been developedextensively in the industry with a wide variety of designs andmanufacturing techniques in attempts to meet performance demands in anextremely cost-competitive environment.

Plastic ball grid array (PBGA) packages have a chip and a laminatedsubstrate enclosed in a plastic housing and are attached to a printedcircuit board (PCB) by solder balls. The laminated substrate includes adielectric layer that often includes fiberglass. The heat from the chipflows through the plastic and the dielectric layer to the solder ballsand then the PCB. However, since the plastic and the dielectric layertypically have low thermal conductivity, the PBGA provides poor heatdissipation.

Quad-Flat-No Lead (QFN) packages have the chip mounted on a copper diepad which is soldered to the PCB. The heat from the chip flows throughthe die pad to the PCB. However, since the lead frame type interposerhas limited routing capability, the QFN package cannot accommodate highinput/output (I/O) chips or passive elements.

Thermal boards provide electrical routing, thermal management andmechanical support for semiconductor devices. Thermal boards usuallyinclude a substrate for signal routing, a heat spreader or heat sink forheat removal, pads for electrical connection to the semiconductor deviceand terminals for electrical connection to the next level assembly. Thesubstrate can be a laminated structure with single layer or multi-layerrouting circuitry and one or more dielectric layers. The heat spreadercan be a metal base, a metal slug or an embedded metal layer.

Thermal boards interface with the next level assembly. For instance, thenext level assembly can be a light fixture with a printed circuit boardand a heat sink. In this instance, an LED package is mounted on thethermal board, the thermal board is mounted on the heat sink, thethermal board/heat sink subassembly and the printed circuit board aremounted in the light fixture and the thermal board is electricallyconnected to the printed circuit board by wires. The substrate routeselectrical signals to the LED package from the printed circuit board andthe heat spreader spreads and transfers heat from the LED package to theheat sink. The thermal board thus provides a critical thermal path forthe LED chip.

U.S. Pat. No. 6,507,102 to Juskey et al. discloses an assembly in whicha composite substrate with fiberglass and cured thermosetting resinincludes a central opening, a heat slug with a square or rectangularshape resembling the central opening is attached to the substrate atsidewalls of the central opening, top and bottom conductive layers areattached to the top and bottom of the substrate and electricallyconnected to one another by plated through-holes through the substrate,a chip is mounted on the heat slug and wire bonded to the top conductivelayer, an encapsulant is molded on the chip and solder balls are placedon the bottom conductive layer.

During manufacture, the substrate is initially a prepreg with B-stageresin placed on the bottom conductive layer, the heat slug is insertedinto the central opening and on the bottom conductive layer and spacedfrom the substrate by a gap, the top conductive layer is mounted on thesubstrate, the conductive layers are heated and pressed towards oneanother so that the resin melts, flows into the gap and solidifies, theconductive layers are patterned to form circuit traces on the substrateand expose the excess resin flash on the heat slug, and the excess resinflash is removed to expose the heat slug. The chip is then mounted onthe heat slug, wire bonded and encapsulated.

The heat flows from the chip through the heat slug to the PCB. However,manually dropping the heat slug into the central opening isprohibitively cumbersome and expensive for high volume manufacture.Furthermore, since the heat slug is difficult to accurately position inthe central opening due to tight lateral placement tolerance, voids andinconsistent bond lines arise between the substrate and the heat slug.The substrate is therefore partially attached to the heat slug, fragiledue to inadequate support by the heat slug and prone to delamination. Inaddition, the wet chemical etch that removes portions of the conductivelayers to expose the excess resin flash also removes portions of theheat slug exposed by the excess resin flash. The heat slug is thereforenon-planar and difficult to bond to. As a result, the assembly suffersfrom high yield loss, poor reliability and excessive cost.

U.S. Pat. No. 6,528,882 to Ding et al. discloses a thermal enhanced ballgrid array package in which the substrate includes a metal core layer.The chip is mounted on a die pad region at the top surface of the metalcore layer, an insulating layer is formed on the bottom surface of themetal core layer, blind vias extend through the insulating layer to themetal core layer, thermal balls fill the blind vias and solder balls areplaced on the substrate and aligned with the thermal balls. The heatfrom the chip flows through the metal core layer to the thermal balls tothe PCB. However, the insulating layer sandwiched between the metal corelayer and the PCB limits the heat flow to the PCB.

U.S. Pat. No. 6,670,219 to Lee et al. discloses a cavity down ball gridarray (CDBGA) package in which a ground plate with a central opening ismounted on a heat spreader to form a thermal dissipating substrate. Asubstrate with a central opening is mounted on the ground plate using anadhesive with a central opening. A chip is mounted on the heat spreaderin a cavity defined by the central opening in the ground plate andsolder balls are placed on the substrate. However, since the solderballs extend above the substrate, the heat spreader does not contact thePCB. As a result, the heat spreader releases the heat by thermalconvection rather than thermal conduction which severely limits the heatdissipation.

U.S. Pat. No. 7,038,311 to Woodall et al. discloses a thermal enhancedBGA package in which a heat sink with an inverted T-like shape includesa pedestal and an expanded base, a substrate with a window opening ismounted on the expanded base, an adhesive attaches the pedestal and theexpanded base to the substrate, a chip is mounted on the pedestal andwire bonded to the substrate, an encapsulant is molded on the chip andsolder balls are placed on the substrate. The pedestal extends throughthe window opening, the substrate is supported by the expanded base andthe solder balls are located between the expanded base and the perimeterof the substrate. The heat from the chip flows through the pedestal tothe expanded base to the PCB. However, since the expanded base mustleave room for the solder balls, the expanded base protrudes below thesubstrate only between the central window and the innermost solder ball.Consequently, the substrate is unbalanced and wobbles and warps duringmanufacture. This creates enormous difficulties with chip mounting, wirebonding and encapsulant molding. Furthermore, the expanded base may bebent by the encapsulant molding and may impede soldering the package tothe next level assembly as the solder balls collapse. As a result, thepackage suffers from high yield loss, poor reliability and excessivecost.

U.S. Patent Application Publication No. 2007/0267642 to Erchak et al.discloses a light emitting device assembly in which a base with aninverted T-like shape includes a substrate, a protrusion and aninsulative layer with an aperture, electrical contacts are mounted onthe insulative layer, a package with an aperture and a transparent lidis mounted on the electrical contacts and an LED chip is mounted on theprotrusion and wire bonded to the substrate. The protrusion is adjacentto the substrate and extends through the apertures in the insulativelayer and the package into the package, the insulative layer is mountedon the substrate, the electrical contacts are mounted on the insulativelayer and the package is mounted on the electrical contacts and spacedfrom the insulative layer. The heat from the chip flows through theprotrusion to the substrate to a heat sink. However, the electricalcontacts are difficult to mount on the insulating layer, difficult toelectrically connect to the next level assembly and fail to providemulti-layer routing.

Conventional packages and thermal boards thus have major deficiencies.For instance, dielectrics with low thermal conductivity such as epoxylimit heat dissipation, whereas dielectrics with higher thermalconductivity such as epoxy filled with ceramic or silicon carbide havelow adhesion and are prohibitively expensive for high volumemanufacture. The dielectric may delaminate during manufacture orprematurely during operation due to the heat. The substrate may havesingle layer circuitry with limited routing capability or multi-layercircuitry with thick dielectric layers which reduce heat dissipation.The heat spreader may be inefficient, cumbersome or difficult tothermally connect to the next level assembly. The manufacturing processmay be unsuitable for low cost, high volume manufacture.

In view of the various development stages and limitations in currentlyavailable packages and thermal boards for high power semiconductordevices, there is a need for a semiconductor chip assembly that is costeffective, reliable, manufacturable, versatile, provides flexible signalrouting and has excellent heat spreading and dissipation.

SUMMARY OF THE INVENTION

The present invention provides a semiconductor chip assembly thatincludes a semiconductor device, a heat spreader, a conductive trace andan adhesive. The semiconductor device is electrically connected to theconductive trace and thermally connected to the heat spreader. The heatspreader includes a thermal post and a base. The thermal post extendsupwardly from the base into a first opening in the adhesive, and thebase extends laterally from the thermal post. The conductive traceincludes a pad, a terminal and a signal post. The signal post extendsupwardly from the terminal into a second opening in the adhesive.

In accordance with an aspect of the present invention, a semiconductorchip assembly includes a semiconductor device, an adhesive, a heatspreader and a conductive trace. The adhesive includes first and secondopenings. The heat spreader includes a thermal post and a base, whereinthe thermal post is adjacent to the base and extends above the base inan upward direction, and the base extends below the thermal post in adownward direction opposite the upward direction and extends laterallyfrom the thermal post in lateral directions orthogonal to the upward anddownward directions. The conductive trace includes a pad, a terminal anda signal post, wherein the signal post extends below the pad and abovethe terminal and an electrically conductive path between the pad and theterminal includes the signal post.

The semiconductor device is above and overlaps the thermal post, iselectrically connected to the pad and thereby electrically connected tothe terminal, and is thermally connected to the thermal post and therebythermally connected to the base. The adhesive is mounted on and extendsabove the base and extends laterally from the thermal post to or beyondthe terminal. The pad extends above the adhesive and the terminalextends below the adhesive. The thermal post extends into the firstopening and the signal post extends into the second opening.Furthermore, the posts have the same thickness and are coplanar with oneanother, and the base and the terminal have the same thickness and arecoplanar with one another.

The conductive trace can include the pad, the terminal, the signal postand a routing line. The routing line can be adjacent to the pad, thesignal post can be adjacent to the routing line and the terminal, extendbelow the pad and the routing line and extend above the terminal, thepad and the routing line can overlap the adhesive, the terminal can beoverlapped by the adhesive, and the signal post can extend through theadhesive. The pad, the terminal, the signal post and the routing cancontact the adhesive, and an electrically conductive path between thepad and the terminal can include the signal post and the routing line.

In accordance with another aspect of the present invention, asemiconductor chip assembly includes a semiconductor device, anadhesive, a heat spreader, a substrate and a conductive trace. Theadhesive includes first and second openings. The heat spreader includesa thermal post and a base, wherein the thermal post is adjacent to thebase and extends above the base in an upward direction, and the baseextends below the thermal post in a downward direction opposite theupward direction and extends laterally from the thermal post in lateraldirections orthogonal to the upward and downward directions. Thesubstrate includes a pad and a dielectric layer, and first and secondapertures extend through the substrate. The conductive trace includesthe pad, a terminal and a signal post, wherein the signal post extendsbelow the pad and above the terminal and an electrically conductive pathbetween the pad and the terminal includes the signal post.

The semiconductor device is above and overlaps the thermal post, iselectrically connected to the pad and thereby electrically connected tothe terminal, and is thermally connected to the thermal post and therebythermally connected to the base. The adhesive is mounted on and extendsabove the base, extends into a first gap in the first aperture betweenthe thermal post and the substrate and into a second gap in the secondaperture between the signal post and the substrate, extends across thedielectric layer in the gaps, extends laterally from the thermal post toor beyond the terminal and is sandwiched between the thermal post andthe dielectric layer, between the signal post and the dielectric layerand between the base and the dielectric layer. The substrate is mountedon the adhesive and extends above the base. The thermal post extendsinto the first opening and the first aperture, and the signal postextends into the second opening and the second aperture. Furthermore,the posts have the same thickness and are coplanar with one another, andthe base and the terminal have the same thickness and are coplanar withone another.

The heat spreader can include a cap that is above and adjacent to andcovers in the upward direction and extends laterally in the lateraldirections from a top of the thermal post. For instance, the cap canhave a rectangular or square shape and the top of the thermal post canhave a circular shape. In this instance, the cap can be sized and shapedto accommodate a thermal contact surface of the semiconductor devicewhereas the top of the thermal post is not sized and shaped toaccommodate the thermal contact surface of the semiconductor device. Thecap can also contact and cover a portion of the adhesive that iscoplanar with and adjacent to the thermal post. The cap can also becoplanar with the pad above the dielectric layer. In addition, thethermal post can thermally connect the base and the cap. The heatspreader can consist of the thermal post and the base or the thermalpost, the base and the cap. The heat spreader can also consist ofcopper, aluminum or copper/nickel/aluminum. In any case, the heatspreader provides heat dissipation and spreading from the semiconductordevice to the next level assembly.

The semiconductor device can be mounted on the heat spreader. Forinstance, the semiconductor device can be mounted on the heat spreaderand the substrate, overlap the thermal post and the pad, be electricallyconnected to the pad using a first solder joint and be thermallyconnected to the heat spreader using a second solder joint.Alternatively, the semiconductor device can be mounted on the heatspreader but not the substrate, overlap the thermal post but not thesubstrate, be electrically connected to the pad using a wire bond and bethermally connected to the heat spreader using a die attach.

The semiconductor device can be a packaged or unpackaged semiconductorchip. For instance, the semiconductor device can be an LED package thatincludes an LED chip, is mounted on the heat spreader and the substrate,overlaps the thermal post and the pad, is electrically connected to thepad using a first solder joint and is thermally connected to the heatspreader using a second solder joint. Alternatively, the semiconductordevice can be a semiconductor chip that is mounted on the heat spreaderbut not the substrate, overlaps the thermal post but not the substrate,is electrically connected to the pad using a wire bond and is thermallyconnected to the heat spreader using a die attach.

The adhesive can contact the thermal post and the dielectric layer inthe first gap, contact the signal post and the dielectric layer in thesecond gap and contact the base, the terminal and the dielectric layeroutside the gaps. The adhesive can also cover and surround the posts inthe lateral directions and conformally coat the sidewalls of the posts.The adhesive can also be coplanar with tops and bottoms of the posts.

The adhesive can extend laterally from the thermal post to or beyond theterminal. For instance, the adhesive and the terminal can extend toperipheral edges of the assembly. In this instance, the adhesive extendslaterally from the thermal post to the terminal. Alternatively, theadhesive can extend to peripheral edges of the assembly and the terminalcan be spaced from the peripheral edges of the assembly. In thisinstance, the adhesive extends laterally from the thermal post beyondthe terminal.

The thermal post can be integral with the base. For instance, thethermal post and the base can be a single-piece metal or include asingle-piece metal at their interface, and the single-piece metal can becopper. The thermal post can also extend through the first aperture. Thethermal post can also be coplanar with the adhesive above the dielectriclayer. The thermal post can also have a cut-off conical shape in whichits diameter decreases as it extends upwardly from the base to its flattop adjacent to the cap.

The signal post can be integral with the terminal. For instance, thesignal post and the terminal can be a single-piece metal or include asingle-piece metal at their interface, and the single-piece metal can becopper. The signal post can also extend through the second aperture. Thesignal post can also be coplanar with the adhesive above the dielectriclayer. The signal post can also have a cut-off conical shape in whichits diameter decreases as it extends upwardly from the terminal to itsflat top adjacent to the routing line.

The base can cover the thermal post in the downward direction, supportthe substrate and be spaced from peripheral edges of the assembly.

The substrate can be spaced from the thermal post and the base. Thesubstrate can also be a laminated structure.

The conductive trace can be spaced from the heat spreader. The pad cancontact the dielectric layer, the terminal can contact the adhesive andthe signal post can contact the adhesive and the dielectric layer.Furthermore, the terminal can be adjacent to and extend below andlaterally from the signal post.

The pad can be an electrical contact for the semiconductor device, theterminal can be an electrical contact for the next level assembly, andthe pad and the terminal can provide vertical signal routing between thesemiconductor device and the next level assembly.

The assembly can be a first-level or second-level single-chip ormulti-chip device. For instance, the assembly can be a first-levelpackage that contains a single chip or multiple chips. Alternatively,the assembly can be a second-level module that contains a single LEDpackage or multiple LED packages, and each LED package can contain asingle LED chip or multiple LED chips.

The present invention provides a method of making a semiconductor chipassembly that includes providing a thermal post, a signal post and abase, mounting an adhesive on the base including inserting the thermalpost into a first opening in the adhesive and the signal post into asecond opening in the adhesive, mounting a conductive layer on theadhesive including aligning the thermal post with a first aperture inthe conductive layer and the signal post with a second aperture in theconductive layer, then flowing the adhesive into and upward in a firstgap located in the first aperture between the thermal post and theconductive layer and in a second gap located in the second aperturebetween the signal post and the conductive layer, solidifying theadhesive, then providing a conductive trace that includes a pad, aterminal, the signal post and a selected portion of the conductivelayer, mounting a semiconductor device on a heat spreader that includesthe thermal post and the base, electrically connecting the semiconductordevice to the conductive trace and thermally connecting thesemiconductor device to the heat spreader.

In accordance with an aspect of the present invention, a method ofmaking a semiconductor chip assembly includes (1) providing a thermalpost, a signal post, a base, an adhesive and a conductive layer, wherein(a) the thermal post is adjacent to the base, extends above the base inan upward direction, extends into a first opening in the adhesive and isaligned with a first aperture in the conductive layer, (b) the signalpost is adjacent to the base, extends above the base in the upwarddirection, extends into a second opening in the adhesive and is alignedwith a second aperture in the conductive layer, (c) the base extendsbelow the posts in a downward direction opposite the upward directionand extends laterally from the posts in lateral directions orthogonal tothe upward and downward directions, (d) the adhesive is mounted on andextends above the base, is sandwiched between the base and theconductive layer and is non-solidified, and (e) the conductive layer ismounted on and extends above the adhesive, then (2) flowing the adhesiveinto and upward in a first gap located in the first aperture between thethermal post and the conductive layer and in a second gap located in thesecond aperture between the signal post and the conductive layer, (3)solidifying the adhesive, then (4) providing a conductive trace thatincludes a pad, a terminal, the signal post and a selected portion ofthe conductive layer, (5) mounting a semiconductor device on a heatspreader that includes the thermal post and the base, wherein thesemiconductor device overlaps the thermal post, (6) electricallyconnecting the semiconductor device to the pad, thereby electricallyconnecting the semiconductor device to the terminal, wherein anelectrically conductive path between the pad and the terminal includesthe signal post, and (7) thermally connecting the semiconductor deviceto the thermal post, thereby thermally connecting the semiconductordevice to the base.

In accordance with another aspect of the present invention, a method ofmaking a semiconductor chip assembly includes (1) providing a thermalpost, a signal post and a base, wherein the thermal post is adjacent toand integral with the base and extends above the base in an upwarddirection, the signal post is adjacent to and integral with the base andextends above the base in the upward direction, and the base extendsbelow the posts in a downward direction opposite the upward directionand extends laterally from the posts in lateral directions orthogonal tothe upward and downward directions, (2) providing an adhesive, whereinfirst and second openings extend through the adhesive, (3) providing aconductive layer, wherein first and second apertures extend through theconductive layer, (4) mounting the adhesive on the base, includinginserting the thermal post into the first opening and the signal postinto the second opening, wherein the adhesive extends above the base,the thermal post extends into the first opening and the signal postextends into the second opening, (5) mounting the conductive layer onthe adhesive, including aligning the thermal post with the firstaperture and the signal post with the second aperture, wherein theconductive layer extends above the adhesive and the adhesive issandwiched between the base and the conductive layer and isnon-solidified, then (6) applying heat to melt the adhesive, (7) movingthe base and the conductive layer towards one another, thereby movingthe thermal post upward in the first aperture, moving the signal postupward in the second aperture and applying pressure to the moltenadhesive between the base and the conductive layer, wherein the pressureforces the molten adhesive to flow into and upward in a first gaplocated in the first aperture between the thermal post and theconductive layer and in a second gap located in the second aperturebetween the signal post and the conductive layer, (8) applying heat tosolidify the molten adhesive, thereby mechanically attaching the postsand the base to the conductive layer, then (9) providing a conductivetrace that includes a pad, a terminal, a routing line and the signalpost, wherein the conductive trace includes a selected portion of theconductive layer and an electrically conductive path between the pad andthe terminal includes the routing line and the signal post, (10)mounting a semiconductor device on a heat spreader that includes thethermal post and the base, wherein the semiconductor device overlaps thethermal post, (11) electrically connecting the semiconductor device tothe pad, thereby electrically connecting the semiconductor device to theterminal, and (12) thermally connecting the semiconductor device to thethermal post, thereby thermally connecting the semiconductor device tothe base.

Mounting the conductive layer can include mounting the conductive layeralone on the adhesive, or alternatively, attaching the conductive layerto a carrier, then mounting the conductive layer and the carrier on theadhesive such that the carrier overlaps the conductive layer and theconductive layer contacts the adhesive and is sandwiched between theadhesive and the carrier, and then, after solidifying the adhesive,removing the carrier and then providing the conductive trace.

In accordance with another aspect of the present invention, a method ofmaking a semiconductor chip assembly includes (1) providing a thermalpost, a signal post, a base, an adhesive and a substrate, wherein (a)the substrate includes a conductive layer and a dielectric layer, (b)the thermal post is adjacent to the base, extends above the base in anupward direction, extends through a first opening in the adhesive andextends into a first aperture in the substrate, (c) the signal post isadjacent to the base, extends above the base in the upward direction,extends through a second opening in the adhesive and extends into asecond aperture in the substrate, (d) the base extends below the postsin a downward direction opposite the upward direction and extendslaterally from the posts in lateral directions orthogonal to the upwardand downward directions, (e) the adhesive is mounted on and extendsabove the base, is sandwiched between the base and the substrate and isnon-solidified, (f) the substrate is mounted on and extends above theadhesive and the conductive layer extends above the dielectric layer,(g) a first gap is located in the first aperture between the thermalpost and the substrate, and (h) a second gap is located in the secondaperture between the signal post and the substrate, then (2) flowing theadhesive into and upward in the gaps, (3) solidifying the adhesive, then(4) mounting a semiconductor device on a heat spreader that includes thethermal post and the base, wherein the semiconductor device overlaps thethermal post, a conductive trace includes a pad, a terminal, the signalpost and a selected portion of the conductive layer and an electricallyconductive path between the pad and the terminal includes the signalpost, (5) electrically connecting the semiconductor device to the pad,thereby electrically connecting the semiconductor device to theterminal, and (6) thermally connecting the semiconductor device to thethermal post, thereby thermally connecting the semiconductor device tothe base.

In accordance with another aspect of the present invention, a method ofmaking a semiconductor chip assembly includes (1) providing a thermalpost, a signal post and a base, wherein the thermal post is adjacent toand integral with the base and extends above the base in an upwarddirection, the signal post is adjacent to and integral with the base andextends above the base in the upward direction, and the base extendsbelow the posts in a downward direction opposite the upward directionand extends laterally from the posts in lateral directions orthogonal tothe upward and downward directions, (2) providing an adhesive, whereinfirst and second openings extend through the adhesive, (3) providing asubstrate that includes a conductive layer and a dielectric layer,wherein first and second apertures extend through the substrate, (4)mounting the adhesive on the base, including inserting the thermal postthrough the first opening and the signal post through the secondopening, wherein the adhesive extends above the base, the thermal postextends through the first opening and the signal post extends throughthe second opening, (5) mounting the substrate on the adhesive,including inserting the thermal post into the first aperture and thesignal post into the second aperture, wherein the substrate extendsabove the adhesive, the conductive layer extends above the dielectriclayer, the thermal post extends through the first opening into the firstaperture, the signal post extends through the second opening into thesecond aperture, the adhesive is sandwiched between the base and thesubstrate and is non-solidified, a first gap is located in the firstaperture between the thermal post and the substrate and a second gap islocated in the second aperture between the signal post and thesubstrate, then (6) applying heat to melt the adhesive, (7) moving thebase and the substrate towards one another, thereby moving the thermalpost upward in the first aperture, moving the signal post upward in thesecond aperture and applying pressure to the molten adhesive between thebase and the substrate, wherein the pressure forces the molten adhesiveto flow into and upward in the gaps and the posts and the moltenadhesive extend above the dielectric layer, (8) applying heat tosolidify the molten adhesive, thereby mechanically attaching the postsand the base to the substrate, then (9) mounting a semiconductor deviceon a heat spreader that includes the thermal post and the base, whereinthe semiconductor device overlaps the post, a conductive trace includesa pad, a terminal, the signal post and a selected portion of theconductive layer and an electrically conductive path between the pad andthe terminal includes the signal post, (10) electrically connecting thesemiconductor device to the pad, thereby electrically connecting thesemiconductor device to the terminal, and (11) thermally connecting thesemiconductor device to the thermal post, thereby thermally connectingthe semiconductor device to the base.

Providing the thermal post, the signal post and the base can includeproviding a metal plate, forming an etch mask on the metal plate thatselectively exposes the metal plate, etching the metal plate in apattern defined by the etch mask, thereby forming a recess in the metalplate that extends into but not through the metal plate, and thenremoving the etch mask, wherein the thermal post includes a firstunetched portion of the metal plate that protrudes above the base and islaterally surrounded by the recess, the signal post includes a secondunetched portion of the metal plate that protrudes above the base and islaterally surrounded by the recess, and the base is an unetched portionof the metal plate below the posts and the recess.

Providing the adhesive can include providing a prepreg with uncuredepoxy, flowing the adhesive can include melting the uncured epoxy andcompressing the uncured epoxy between the base and the substrate, andsolidifying the adhesive can include curing the molten uncured epoxy.

Providing the heat spreader can include providing a cap on the thermalpost that is above and adjacent to and covers in the upward directionand extends laterally in the lateral directions from a top of thethermal post after solidifying the adhesive and before mounting thesemiconductor device.

Providing the pad can include removing selected portions of theconductive layer after solidifying the adhesive.

Providing the pad can also include grinding the posts, the adhesive andthe conductive layer after solidifying the adhesive such that the posts,the adhesive and the conductive layer are laterally aligned with oneanother at a top lateral surface that faces in the upward direction, andthen removing selected portions of the conductive layer such that thepad includes selected portions of the conductive layer. The grinding caninclude grinding the adhesive without grinding the posts and thengrinding the posts, the adhesive and the conductive layer. The removingcan include applying a wet chemical etch to the conductive layer usingan etch mask that defines the pad.

Providing the pad can also include depositing a second conductive layeron the posts, the adhesive and the conductive layer after the grindingand then removing selected portions of the conductive layers such thatthe pad includes selected portions of the conductive layers. Depositingthe second conductive layer can include electrolessly plating a firstplated layer on the posts, the adhesive and the conductive layer andthen electroplating a second plated layer on the first plated layer. Theremoving can include applying the wet chemical etch to the conductivelayers using the etch mask to define the pad.

Providing the terminal can include removing selected portions of thebase after solidifying the adhesive. The removing can include applying awet chemical etch to the base using an etch mask to define the terminalsuch that the terminal includes an unetched portion of the base that isadjacent to the signal post and is spaced and separated from and nolonger part of the base. Thus, the pad and the terminal can be formedsimultaneously using the same wet chemical etch and different etchmasks.

Providing the cap can include removing selected portions of the secondconductive layer. Providing the cap can also include the grinding andthen removing selected portions of the second conductive layer using theetch mask to define the cap such that the cap includes selected portionsof the second conductive layer. Thus, the pad and the cap can be formedsimultaneously using the same grinding, wet chemical etch and etch mask.

Flowing the adhesive can include filling the gaps with the adhesive.Flowing the adhesive can also include squeezing the adhesive through thegaps, above the posts and the substrate and on top surface portions ofthe posts and the substrate adjacent to the gaps.

Solidifying the adhesive can include mechanically bonding the posts andthe base to the substrate.

Mounting the semiconductor device can include mounting the semiconductordevice on the cap. Mounting the semiconductor device can also includepositioning the semiconductor device above and overlapping the thermalpost, the cap, the first opening and the first aperture withoutoverlapping the signal post, the second opening or the second aperture.

Mounting the semiconductor device can include providing a first solderjoint between an LED package that includes an LED chip and the pad and asecond solder joint between the LED package and the cap, electricallyconnecting the semiconductor device can include providing the firstsolder joint between the LED package and the pad, and thermallyconnecting the semiconductor device can include providing the secondsolder joint between the LED package and the cap.

Mounting the semiconductor device can include providing a die attachbetween a semiconductor chip and the cap, electrically connecting thesemiconductor device can include providing a wire bond between the chipand the pad, and thermally connecting the semiconductor device caninclude providing the die attach between the chip and the cap.

The adhesive can contact the posts, the base, the cap and the dielectriclayer, cover the substrate in the downward direction, cover and surroundthe posts in the lateral directions and extend to peripheral edges ofthe assembly after the assembly is manufactured and detached from otherassemblies in a batch.

The base can cover the semiconductor device, the thermal post and thecap in the downward direction, support the substrate and be spaced fromperipheral edges of the assembly after the assembly is manufactured anddetached from other assemblies in a batch.

The present invention has numerous advantages. The heat spreader canprovide excellent heat spreading and heat dissipation without heat flowthrough the adhesive. As a result, the adhesive can be a low costdielectric with low thermal conductivity and not prone to delamination.The thermal post and the base can be integral with one another, therebyenhancing reliability. The cap can be customized for the semiconductordevice, thereby enhancing the thermal connection. The adhesive can besandwiched between the posts and the substrate and between the base andthe substrate, thereby providing a robust mechanical bond between theheat spreader and the substrate. The conductive trace can provide signalrouting with simple circuitry patterns or flexible multi-layer signalrouting with complex circuitry patterns. The conductive trace can alsoprovide vertical signal routing between the pad above the dielectriclayer and the terminal below the adhesive. The base can providemechanical support for the substrate, thereby preventing warping. Theassembly can be manufactured using low temperature processes whichreduces stress and improves reliability. The assembly can also bemanufactured using well-controlled processes which can be easilyimplemented by circuit board, lead frame and tape manufacturers.

These and other features and advantages of the present invention will befurther described and more readily apparent from a review of thedetailed description of the preferred embodiments which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the preferred embodiments of thepresent invention can best be understood when read in conjunction withthe following drawings, in which:

FIGS. 1A-1F are cross-sectional views showing a method of making a postand a base in accordance with an embodiment of the present invention;

FIGS. 1G and 1H are top and bottom views, respectively, corresponding toFIG. 1F;

FIGS. 2A and 2B are cross-sectional views showing a method of making anadhesive in accordance with an embodiment of the present invention;

FIGS. 2C and 2D are top and bottom views, respectively, corresponding toFIG. 2B;

FIGS. 3A and 3B are cross-sectional views showing a method of making asubstrate in accordance with an embodiment of the present invention;

FIGS. 3C and 3D are top and bottom views, respectively, corresponding toFIG. 3B;

FIGS. 4A-4L are cross-sectional views showing a method of making athermal board with a substrate on an adhesive in accordance with anembodiment of the present invention;

FIGS. 4M and 4N are top and bottom views, respectively, corresponding toFIG. 4L;

FIGS. 5A, 5B and 5C are cross-sectional, top and bottom views,respectively, of a thermal board with a conductive trace on an adhesivein accordance with an embodiment of the present invention;

FIGS. 6A, 6B and 6C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard and an LED package with backside contacts accordance with anembodiment of the present invention;

FIGS. 7A, 7B and 7C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard and an LED package with lateral leads in accordance with anembodiment of the present invention; and

FIGS. 8A, 8B and 8C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard and a semiconductor chip in accordance with an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1A-1D are cross-sectional views showing a method of making athermal post, a signal post and a base in accordance with an embodimentof the present invention, and FIGS. 1E and 1F are top and bottom views,respectively, corresponding to FIG. 1D.

FIG. 1A. is a cross-sectional view of metal plate 10 which includesopposing major surfaces 12 and 14. Metal plate 10 is illustrated as acopper plate with a thickness of 330 microns. Copper has high thermalconductivity, good bondability and low cost. Metal plate 10 can bevarious metals such as copper, aluminum, alloy 42, iron, nickel, silver,gold, combinations thereof, and alloys thereof.

FIG. 1B is a cross-sectional view of etch mask 16 and cover mask 18formed on metal plate 10. Etch mask 16 and cover mask 18 are illustratedas photoresist layers which are deposited on metal plate 10 using dryfilm lamination in which hot rolls simultaneously press photoresistlayers 16 and 18 onto surfaces 12 and 14, respectively. Wet spin coatingand curtain coating are also suitable deposition techniques. A reticle(not shown) is positioned proximate to photoresist layer 16. Thereafter,photoresist layer 16 is patterned by selectively applying light throughthe reticle so that the photoresist portions exposed to the light arerendered insoluble, applying a developer solution to remove thephotoresist portions that are unexposed to the light and remain solubleand then hard baking, as is conventional. As a result, photoresist layer16 has a pattern that selectively exposes surface 12, and photoresistlayer 18 remains unpatterned and covers surface 14.

FIG. 1C is a cross-sectional view of recess 20 formed into but notthrough metal plate 10 by etching metal plate 10 in the pattern definedby etch mask 16. The etching is illustrated as a front-side wet chemicaletch. For instance, the structure can be inverted so that etch mask 16faces downward and cover mask 18 faces upward as a bottom spray nozzle(not shown) that faces etch mask 16 upwardly sprays the wet chemicaletch on metal plate 10 and etch mask 16 while a top spray nozzle (notshown) that faces cover mask 18 is deactivated so that gravity assistswith removing the etched byproducts. Alternatively, the structure can bedipped in the wet chemical etch since cover mask 18 provides back-sideprotection. The wet chemical etch is highly selective of copper andetches 300 microns into metal plate 10. As a result, recess 20 extendsfrom surface 12 into but not through metal plate 10, is spaced fromsurface 14 by 30 microns and has a depth of 300 microns. The wetchemical etch also laterally undercuts metal plate 10 beneath etch mask16. A suitable wet chemical etch can be provided by a solutioncontaining alkaline ammonia or a dilute mixture of nitric andhydrochloric acid. Likewise, the wet chemical etch can be acidic oralkaline. The optimal etch time for forming recess 20 withoutexcessively exposing metal plate 10 to the wet chemical etch can beestablished through trial and error.

FIGS. 1D, 1E and 1F are cross-sectional, top and bottom views,respectively, of metal plate 10 after etch mask 16 and cover mask 18 areremoved. The photoresist layers are stripped using a solvent, such as astrong alkaline solution containing potassium hydroxide with a pH of 14,that is highly selective of photoresist with respect to copper.

Metal plate 10 as etched includes thermal post 22, signal post 24 andbase 26.

Thermal post 22 is a first unetched portion of metal plate 10 defined byetch mask 16. Thermal post 22 is adjacent to and integral with andprotrudes above base 26 and is laterally surrounded by recess 20.Thermal post 22 has a height of 300 microns (recess 20 depth), adiameter at its top surface (circular portion of surface 12) of 1000microns and a diameter at its bottom (circular portion adjacent to base26) of 1100 microns. Thus, thermal post 22 has a cut-off conical shape(resembling a frustum) with tapered sidewalls in which its diameterdecreases as it extends upwardly from base 26 to its flat circular topsurface. The tapered sidewalls arise from the lateral undercutting bythe wet chemical etch beneath etch mask 16. The top surface isconcentrically disposed within a periphery of the bottom (shown inphantom in FIG. 1E).

Signal post 24 is a second unetched portion of metal plate 10 defined byetch mask 16. Signal post 24 is adjacent to and integral with andprotrudes above base 26 and is laterally surrounded by recess 20 andlaterally spaced from thermal post 22. Signal post 24 has a height of300 microns (recess 20 depth), a diameter at its top surface (circularportion of surface 12) of 300 microns and a diameter at its bottom(circular portion adjacent to base 26) of 400 microns. Thus, signal post24 has a cut-off conical shape (resembling a frustum) with taperedsidewalls in which its diameter decreases as it extends upwardly frombase 26 to its flat circular top surface. The tapered sidewalls arisefrom the lateral undercutting by the wet chemical etch beneath etch mask16. The top surface is concentrically disposed within a periphery of thebottom (shown in phantom in FIG. 1E).

Base 26 is an unetched portion of metal plate 10 that is below posts 22and 24, extends laterally from posts 22 and 24 in a lateral plane (withlateral directions such as left and right) and has a thickness of 30microns (330−300).

Thermal post 22, signal post 24 and base 26 can be treated to improvebondability to epoxy and solder. For instance, posts 22 and 24 and base26 can be chemically oxidized or microetched to provide roughersurfaces.

Thermal post 22, signal post 24 and base 26 are illustrated as asubtractively formed single-piece metal (copper). Thermal post 22,signal post 24 and base 26 can also be a stamped single-piece metalformed by stamping metal plate 10 with a contact piece with a firstrecess or hole that defines thermal post 22 and a second recess or holethat defines signal post 24. Posts 22 and 24 can also be formedadditively by depositing posts 22 and 24 on base 26 usingelectroplating, chemical vapor deposition (CVD), physical vapordeposition (PVD) and so on, for instance by electroplating a solderthermal post 22 and a solder signal post 24 on a copper base 26, inwhich case thermal post 22 and base 26 have a metallurgical interfaceand are adjacent to but not integral with one another and signal post 24and base 26 have a metallurgical interface and are adjacent to but notintegral with one another. Posts 22 and 24 can also be formedsemi-additively, for instance by depositing upper portions of posts 22and 24 on etch-defined lower portions of posts 22 and 24. Posts 22 and24 and base 26 can also be formed semi-additively by depositingconformal upper portions of posts 22 and 24 and base 26 on etch-definedlower portions of posts 22 and 24 and base 26. Posts 22 and 24 can alsobe sintered to base 26.

FIGS. 2A and 2B are cross-sectional views showing a method of making anadhesive in accordance with an embodiment of the present invention, andFIGS. 2C and 2D are top and bottom views, respectively, corresponding toFIG. 2B.

FIG. 2A is a cross-sectional view of adhesive 28. Adhesive 28 isillustrated as a prepreg with B-stage uncured epoxy provided as anon-solidified unpatterned sheet with a thickness of 180 microns.

Adhesive 28 can be various dielectric films or prepregs formed fromnumerous organic or inorganic electrical insulators. For instance,adhesive 28 can initially be a prepreg in which thermosetting epoxy inresin form impregnates a reinforcement and is partially cured to anintermediate stage. The epoxy can be FR-4 although other epoxies such aspolyfunctional and bismaleimide triazine (BT) are suitable. For specificapplications, cyanate esters, polyimide and PTFE are also suitableepoxies. The reinforcement can be E-glass although other reinforcementssuch as S-glass, D-glass, quartz, kevlar aramid and paper are suitable.The reinforcement can also be woven, non-woven or random microfiber. Afiller such as silica (powdered fused quartz) can be added to theprepreg to improve thermal conductivity, thermal shock resistance andthermal expansion matching. Commercially available prepregs such asSPEEDBOARD C prepreg by W.L. Gore & Associates of Eau Claire, Wis. aresuitable.

FIGS. 2B, 2C and 2D are cross-sectional, top and bottom views,respectively, of adhesive 28 with openings 30 and 32. Opening 30 is afirst window that extends through adhesive 28 and has a diameter of 1150microns, and opening 32 is a second window that extends through adhesive28 and has a diameter of 450 microns. Openings 30 and 32 are formed bymechanical drilling through the prepreg and can be formed by othertechniques such as punching and stamping.

FIGS. 3A and 3B are cross-sectional views showing a method of making asubstrate in accordance with an embodiment of the present invention, andFIGS. 3C and 3D are top and bottom views, respectively, corresponding toFIG. 3B.

FIG. 3A is a cross-sectional view of substrate 34 that includesconductive layer 36 and dielectric layer 38. Conductive layer 36 is anelectrical conductor that contacts and extends above dielectric layer38, and dielectric layer 38 is an electrical insulator. For instance,conductive layer 36 is an unpatterned copper sheet with a thickness of30 microns, and dielectric layer 38 is epoxy with a thickness of 150microns.

FIGS. 3B, 3C and 3D are cross-sectional, top and bottom views,respectively, of substrate 34 with apertures 40 and 42. Aperture 40 is afirst window that extends through substrate 34 and has a diameter of1150 microns, and aperture 42 is a second window that extends throughsubstrate 34 and has a diameter of 450 microns. Apertures 40 and 42 areformed by mechanical drilling through conductive layer 36 and dielectriclayer 38 and can be formed with other techniques such as punching andstamping. Preferably, opening 30 and aperture 40 have the same diameterand are formed in the same manner with the same drill bit at the samedrilling station, and opening 32 and aperture 42 have the same diameterand are formed in the same manner with the same drill bit at the samedrilling station.

Substrate 34 is illustrated as a laminated structure. Substrate 34 canbe other electrical interconnects such as a ceramic board or a printedcircuit board. Likewise, substrate 34 can include additional layers ofembedded circuitry.

FIGS. 4A-4L are cross-sectional views showing a method of making athermal board that includes thermal post 22, signal post 24, base 26,adhesive 28 and substrate 34 in accordance with an embodiment of thepresent invention, and FIGS. 4M and 4N are top and bottom views,respectively, corresponding to FIG. 4L.

FIG. 4A is a cross-sectional view of the structure with adhesive 28mounted on base 26. Adhesive 28 is mounted by lowering it onto base 26as thermal post 22 is inserted into and through and upwards in opening30 and signal post 24 is inserted into and through and upwards inopening 32. Adhesive 28 eventually contacts and rests on base 26.Preferably, thermal post 22 is inserted into and extends through opening30 without contacting adhesive 28 and is aligned with and centrallylocated within opening 30, and signal post 24 is inserted into andextends through opening 32 without contacting adhesive 28 and is alignedwith and centrally located within opening 32.

FIG. 4B is a cross-sectional view of the structure with substrate 34mounted on adhesive 28. Substrate 34 is mounted by lowering it ontoadhesive 28 as thermal post 22 is inserted into and upwards in aperture40 and signal post 24 is inserted into and upwards in aperture 42.Substrate 34 eventually contacts and rests on adhesive 28.

Thermal post 22 is inserted into but not through aperture 40 withoutcontacting substrate 34 and is aligned with and centrally located withinaperture 40. As a result, gap 44 is located in aperture 40 betweenthermal post 22 and substrate 34. Gap 44 laterally surrounds thermalpost 22 and is laterally surrounded by substrate 34. In addition,opening 30 and aperture 40 are precisely aligned with one another andhave the same diameter.

Signal post 24 is inserted into but not through aperture 42 withoutcontacting substrate 34 and is aligned with and centrally located withinaperture 42. As a result, gap 46 is located in aperture 42 betweensignal post 24 and substrate 34. Gap 46 laterally surrounds signal post24 and is laterally surrounded by substrate 34. In addition, opening 32and aperture 42 are precisely aligned with one another and have the samediameter.

At this stage, substrate 34 is mounted on and contacts and extends aboveadhesive 28. Thermal post 22 extends through opening 30 into aperture 40to dielectric layer 38, is 60 microns below the top surface ofconductive layer 36 and is exposed through aperture 40 in the upwarddirection. Signal post 24 extends through opening 32 into aperture 42 todielectric layer 38, is 60 microns below the top surface of conductivelayer 36 and is exposed through aperture 42 in the upward direction.Adhesive 28 contacts and is sandwiched between base 26 and substrate 34,contacts dielectric layer 38 but is spaced from conductive layer 36 andremains a non-solidified prepreg with B-stage uncured epoxy, and gaps 44and 46 are filled with air.

FIG. 4C is a cross-sectional view of the structure with adhesive 28 ingaps 44 and 46. Adhesive 28 is flowed into gaps 44 and 46 by applyingheat and pressure. In this illustration, adhesive 28 is forced into gaps44 and 46 by applying downward pressure to conductive layer 36 and/orupward pressure to base 26, thereby moving base 26 and substrate 34towards one another and applying pressure to adhesive 28 whilesimultaneously applying heat to adhesive 28. Adhesive 28 becomescompliant enough under the heat and pressure to conform to virtually anyshape. As a result, adhesive 28 sandwiched between base 26 and substrate34 is compressed, forced out of its original shape and flows into andupward in gaps 44 and 46. Base 26 and substrate 34 continue to movetowards one another and adhesive 28 eventually fills gaps 44 and 46.Moreover, adhesive 28 remains sandwiched between and continues to fillthe reduced space between base 26 and substrate 34.

For instance, base 26 and conductive layer 36 can be disposed betweentop and bottom platens (not shown) of a press. In addition, a top cullplate and top buffer paper (not shown) can be sandwiched betweenconductive layer 36 and the top platen, and a bottom cull plate andbottom buffer paper (not shown) can be sandwiched between base 26 andthe bottom platen. The stack includes the top platen, top cull plate,top buffer paper, substrate 34, adhesive 28, base 26, bottom bufferpaper, bottom cull plate and bottom platen in descending order.Furthermore, the stack may be positioned on the bottom platen by toolingpins (not shown) that extend upward from the bottom platen throughregistration holes (not shown) in base 26.

The platens are heated and move towards one another, thereby applyingheat and pressure to adhesive 28. The cull plates disperse the heat fromthe platens so that it is more uniformly applied to base 26 andsubstrate 34 and thus adhesive 28, and the buffer papers disperse thepressure from the platens so that it is more uniformly applied to base26 and substrate 34 and thus adhesive 28. Initially, dielectric layer 38contacts and presses down on adhesive 28. As the platen motion and heatcontinue, adhesive 28 between base 26 and substrate 34 is compressed,melted and flows into and upward in gaps 44 and 46 and across dielectriclayer 38 to conductive layer 36. For instance, the uncured epoxy ismelted by the heat and the molten uncured epoxy is squeezed by thepressure into gaps 44 and 46, however the reinforcement and the fillerremain between base 26 and substrate 34. Adhesive 28 elevates morerapidly than thermal post 22 in aperture 40 and fills gap 44, andelevates more rapidly than signal post 24 in aperture 42 and fills gap46. Adhesive 28 also rises slightly above gaps 44 and 46, overflows ontothe top surfaces of thermal post 22 and conductive layer 36 adjacent togap 44 and overflows onto the top surfaces of signal post 24 andconductive layer 36 adjacent to gap 46 before the platen motion stops.This may occur due to the prepreg being slightly thicker than necessary.As a result, adhesive 28 creates a thin coating on the top surfaces ofthermal post 22 and signal post 24. The platen motion is eventuallyblocked by posts 22 and 24 and the platens become stationary butcontinue to apply heat to adhesive 28.

The upward flow of adhesive 28 in gaps 44 and 46 is shown by the thickupward arrows, the upward motion of posts 22 and 24 and base 26 relativeto substrate 34 is shown by the thin upward arrows, and the downwardmotion of substrate 34 relative to posts 22 and 24 and base 26 is shownby the thin downward arrows.

FIG. 4D is a cross-sectional view of the structure with adhesive 28solidified.

For instance, the platens continue to clamp thermal post 22, signal post24 and base 26 and apply heat after the platen motion stops, therebyconverting the B-stage molten uncured epoxy into C-stage cured orhardened epoxy. Thus, the epoxy is cured in a manner similar toconventional multi-layer lamination. After the epoxy is cured, theplatens move away from one another and the structure is released fromthe press.

Adhesive 28 as solidified provides a secure robust mechanical bondbetween thermal post 22 and substrate 34, between signal post 24 andsubstrate 34 and between base 26 and substrate 34. Adhesive 28 canwithstand normal operating pressure without distortion or damage and isonly temporarily distorted under unusually high pressure. Furthermore,adhesive 28 can absorb thermal expansion mismatch between thermal post22 and substrate 34, between signal post 24 and substrate 34 and betweenbase 26 and substrate 34.

At this stage, thermal post 22, signal post 24 and conductive layer 36are essentially coplanar with one another and adhesive 28 and conductivelayer 36 extend to a top surface that faces in the upward direction. Forinstance, adhesive 28 between base 26 and dielectric layer 38 has athickness of 120 microns which is 60 microns less than its initialthickness of 180 microns, thermal post 22 ascends 60 microns in aperture40, signal post 24 ascends 60 microns in aperture 42 and substrate 34descends 60 microns relative to posts 22 and 24. The 300 micron heightof thermal post 22 and of signal post 24 is essentially the same as thecombined height of conductive layer 36 (30 microns), dielectric layer 38(150 microns) and the underlying adhesive 28 (120 microns). Furthermore,thermal post 22 continues to be centrally located in opening 30 andaperture 40 and spaced from substrate 34, signal post 24 continues to becentrally located in opening 32 and aperture 42 and spaced fromsubstrate 34 and adhesive 28 fills the space between base 26 andsubstrate 34 and fills gaps 44 and 46. For instance, gap 44 (as well asadhesive 28 between thermal post 22 and substrate 34) has a width of 75microns ((1150−1000)/2) at the top surface of thermal post 22, and gap46 (as well as adhesive 28 between signal post 24 and substrate 34) hasa width of 75 microns ((450−300)/2) at the top surface of signal post24. Adhesive 28 extends across dielectric layer 38 in gaps 44 and 46.That is, adhesive 28 in gap 44 extends in the upward and downwarddirections across the thickness of dielectric layer 38 at the outersidewall of gap 44, and adhesive 28 in gap 46 extends in the upward anddownward directions across the thickness of dielectric layer 38 at theouter sidewall of gap 46. Adhesive 28 also includes thin top portionsabove gaps 44 and 46 that contact the top surfaces of posts 22 and 24and conductive layer 36 and extends above posts 22 and 24 by 10 microns.

FIG. 4E is a cross-sectional view of the structure after upper portionsof thermal post 22, signal post 24, adhesive 28 and conductive layer 36are removed.

Thermal post 22, signal post 24, adhesive 28 and conductive layer 36have their upper portions removed by grinding. For instance, a rotatingdiamond sand wheel and distilled water are applied to the top of thestructure. Initially, the diamond sand wheel grinds only adhesive 28. Asthe grinding continues, adhesive 28 becomes thinner as its grindedsurface migrates downwardly. Eventually the diamond sand wheel contactsposts 22 and 24 and conductive layer 36 (not necessarily at the sametime), and as a result, begins to grind posts 22 and 24 and conductivelayer 36 as well. As the grinding continues, posts 22 and 24, adhesive28 and conductive layer 36 become thinner as their grinded surfacesmigrate downwardly. The grinding continues until the desired thicknesshas been removed. Thereafter, the structure is rinsed in distilled waterto remove contaminants.

The grinding removes a 25 micron thick upper portion of adhesive 28, a15 micron thick upper portion of thermal post 22, a 15 micron thickupper portion of signal post 24 and a 15 micron thick upper portion ofconductive layer 36. The decreased thickness does not appreciably affectthermal post 22, signal post 24 or adhesive 28. However, itsubstantially reduces the thickness of conductive layer 36 from 30microns to 15 microns.

At this stage, thermal post 22, signal post 24, adhesive 28 andconductive layer 36 are coplanar with one another at a smoothed lappedlateral top surface that is above dielectric layer 38 and faces in theupward direction. Likewise, thermal post 22, signal post 24 and adhesive28 are coplanar with one another at base 26.

FIG. 4F is a cross-sectional view of the structure with conductive layer50 deposited on thermal post 22, signal post 24, adhesive 28 andconductive layer 36.

Conductive layer 50 contacts thermal post 22, signal post 24, adhesive28 and conductive layer 36 and covers them in the upward direction. Forinstance, the structure is dipped in an activator solution to renderadhesive 28 catalytic to electroless copper, then a first copper layeris electrolessly plated on thermal post 22, signal post 24, adhesive 28and conductive layer 36, and then a second copper layer is electroplatedon the first copper layer. The first copper layer has a thickness of 2microns, the second copper layer has a thickness of 13 microns, andconductive layer 50 has a thickness of 15 microns. As a result,conductive layer 36 essentially grows and has a thickness of 30 microns(15+15). Thus, conductive layer 50 serves as a cover layer for thermalpost 22 and signal post 24 and a build-up layer for conductive layer 36.Thermal post 22, signal post 24 and conductive layer 50, and conductivelayers 36 and 50 are shown as a single layer for convenience ofillustration. The boundary (shown in phantom) between thermal post 22and conductive layer 50, between signal post 24 and conductive layer 50and between conductive layers 36 and 50 may be difficult or impossibleto detect since copper is plated on copper. However, the boundarybetween adhesive 28 and conductive layer 50 is clear.

FIG. 4G is a cross-sectional view of the structure with etch mask 52 andetch mask 54 formed on the top and bottom surfaces, respectively, of thestructure. Etch masks 52 and 54 are illustrated as photoresist layerssimilar to photoresist layer 16. Photoresist layer 52 has a pattern thatselectively exposes conductive layer 50, and photoresist layer 54 has apattern that selectively exposes base 26.

FIG. 4H is a cross-sectional view of the structure with selectedportions of conductive layers 36 and 50 removed by etching conductivelayers 36 and 50 in the pattern defined by etch mask 52, and selectedportions of base 26 removed by etching base 26 in the pattern defined byetch mask 54. The etching is a front-side and back-side wet chemicaletch similar to the etch applied to metal plate 10. For instance, a topspray nozzle (not shown) and a bottom spray nozzle (not shown) can spraythe wet chemical etch on the top and bottom of the structure, or thestructure can be dipped in the wet chemical etch. The wet chemical etchetches through conductive layers 36 and 50 to expose adhesive 28 anddielectric layer 38 and converts conductive layers 36 and 50 fromunpatterned into patterned layers. The wet chemical etch also etchesthrough base 26 to expose adhesive 28.

FIG. 4I is a cross-sectional view of the structure after etch masks 52and 54 are removed. Photoresist layers 52 and 54 can be stripped in thesame manner as photoresist layers 16 and 18.

Conductive layers 36 and 50 as etched include pad 56 and routing line58, and conductive layer 50 as etched includes cap 60. Pad 56 androuting line 58 are unetched portions of conductive layers 36 and 50defined by etch mask 52, and cap 60 is an unetched portion of conductivelayer 50 defined by etch mask 52. Thus, conductive layers 36 and 50 area patterned layer that includes pad 56 and routing line 58 and excludescap 60. Furthermore, routing line 58 is a copper trace that contacts andextends above dielectric layer 38 and is adjacent to and electricallyconnects signal post 24 and pad 56.

Base 26 as etched includes base 26, reduced to its central portion, andterminal 62. Base 26 is an unetched portion of base 26 defined by etchmask 54 and extends laterally beyond thermal post 22 by 1000 microns inthe lateral directions, and terminal 62 is an unetched portion of base26 defined by etch mask 54 that is adjacent to and extends below andlaterally from signal post 24 and contacts and extends below adhesive28. Base 26 remains an unpatterned layer, and a patterned layer that islaterally spaced from and outside the periphery of base 26 includesterminal 62. Thus, terminal 62 is spaced and separated from and nolonger a part of base 26. Furthermore, signal post 24 is adjacent to andelectrically connects routing line 58 and terminal 62.

Conductive trace 64 is provided by signal post 24, pad 56, routing line58 and terminal 62. Similarly, an electrically conductive path betweenpad 56 and terminal 62 is signal post 24 and routing line 58. Conductivetrace 64 provides vertical (top to bottom) routing from pad 56 toterminal 62. Conductive trace 64 is not be limited to thisconfiguration. For instance, the electrically conductive path caninclude vias that extend through dielectric layer 38 and additionalrouting lines (above and/or below dielectric layer 38) as well aspassive components such as resistors and capacitors mounted onadditional pads.

Heat spreader 66 includes thermal post 22, base 26 and cap 60. Thermalpost 22 and base 26 are integral with one another. Cap 60 is above andadjacent to and covers in the upward direction and extends laterally inthe lateral directions from the top of thermal post 22. Cap 60 ispositioned so that thermal post 22 is centrally located within itsperiphery. Cap 60 also contacts the underlying portion of adhesive 28that is coplanar with and adjacent to and laterally surrounds thermalpost 22 and covers this portion in the upward direction.

Heat spreader 66 is essentially a heat slug with an inverted T-likeshape that includes a pedestal (thermal post 22), wings (base 26portions that extend laterally from the pedestal) and a thermal pad (cap60).

FIG. 4J is a cross-sectional view of the structure with solder mask 68formed on adhesive 28, dielectric layer 38, conductive layer 50 and cap60 and solder mask 70 formed on base 26, adhesive 28 and terminal 62.

Solder mask 68 is an electrically insulative layer that is selectivelypatterned to expose pad 56 and cap 60 and cover routing line 58 and theexposed portions of adhesive 28 and dielectric layer 38 in the upwarddirection. Solder mask 68 has a thickness of 25 microns above pad 56 andcap 60 and extends 55 microns (30+25) above dielectric layer 38.

Solder mask 70 is an electrically insulative layer that is selectivelypatterned to expose base 26 and terminal 62 and cover the exposedportions of adhesive 28 in the downward direction. Solder mask 70 has athickness of 25 microns below base 26 and terminal 62 and extends 55microns (30+25) below adhesive 28.

Solder masks 68 and 70 can initially be a photoimageable liquid resinthat is dispensed on the structure. Thereafter, solder masks 68 and 70are patterned by selectively applying light through reticles (not shown)so that the solder mask portions exposed to the light are renderedinsoluble, applying a developer solution to remove the solder maskportions that are unexposed to the light and remain soluble and thenhard baking, as is conventional.

FIG. 4K is a cross-sectional view of the structure with plated contacts72 formed on base 26, pad 56, cap 60 and terminal 62.

Plated contacts 72 are thin spot plated metal coatings that contact base26 and terminal 62 and cover their exposed portions in the downwarddirection and contact pad 56 and cap 60 and cover their exposed portionsin the upward direction. For instance, a nickel layer is electrolesslyplated on base 26, pad 56, cap 60 and terminal 62, and then a gold layeris electrolessly plated on the nickel layer. The buried nickel layer hasa thickness of 3 microns, the gold surface layer has a thickness of 0.5microns, and plated contacts 72 have a thickness of 3.5 microns.

Base 26, pad 56, cap 60 and terminal 62 treated with plated contacts 72as a surface finish have several advantages. The buried nickel layerprovides the primary mechanical and electrical and/or thermalconnection, and the gold surface layer provides a wettable surface tofacilitate solder reflow. Plated contacts 72 also protect base 26, pad56, cap 60 and terminal 62 from corrosion. Plated contacts 72 caninclude a wide variety of metals to accommodate the external connectionmedia. For instance, a silver surface layer plated on a buried nickellayer can accommodate a solder joint or a wire bond.

Base 26, pad 56, cap 60 and terminal 62 treated with plated contacts 72are shown as single layers for convenience of illustration. The boundary(not shown) between plated contacts 72 and base 26, pad 56, cap 60 andterminal 62 occurs at the copper/nickel interface.

At this stage, the manufacture of thermal board 74 can be consideredcomplete.

FIGS. 4L, 4M and 4N are cross-sectional, top and bottom views,respectively, of thermal board 74 after it is detached at peripheraledges along cut lines from a support frame and/or adjacent thermalboards in a batch.

Thermal board 74 includes adhesive 28, substrate 34, conductive trace64, heat spreader 66 and solder masks 68 and 70. Substrate 34 includesdielectric layer 38. Conductive trace 64 includes signal post 24, pad56, routing line 58 and terminal 62. Heat spreader 66 includes thermalpost 22, base 26 and cap 60.

Thermal post 22 extends through opening 30 and into aperture 40, remainscentrally located within opening 30 and aperture 40 and is coplanar atits top with an adjacent portion of adhesive 28 above dielectric layer38 and at its bottom with an adjacent portion of adhesive 28 thatcontacts base 26. Thermal post 22 retains its cut-off conical shape withtapered sidewalls in which its diameter decreases as it extends upwardlyfrom base 26 to its flat circular top adjacent to cap 60.

Signal post 24 extends through opening 32 and into aperture 42, remainscentrally located within opening 32 and aperture 42 and is coplanar atits top with an adjacent portion of adhesive 28 above dielectric layer38 and at its bottom with an adjacent portion of adhesive 28 thatcontacts terminal 62. Signal post 24 retains its cut-off conical shapewith tapered sidewalls in which its diameter decreases as it extendsupwardly from terminal 62 to its flat circular top adjacent to routingline 58.

Base 26 covers thermal post 22 and cap 60 in the downward direction andis spaced from the peripheral edges of thermal board 74.

Cap 60 is above and adjacent to and thermally connected to thermal post22, covers the top of thermal post 22 in the upward direction andlaterally extends from the top of thermal post 22 in the lateraldirections. Cap 60 also contacts and covers in the upward direction aportion of adhesive 28 that is coplanar with and adjacent to andlaterally surrounds thermal post 22. Cap 60 is also coplanar with pad56.

Adhesive 28 is mounted on and extends above base 26, contacts and issandwiched between and fills the space between thermal post 22 anddielectric layer 38 in gap 44, contacts and is sandwiched between andfills the space between signal post 24 and dielectric layer 38 in gap46, contacts and is sandwiched between and fills the space between base26 and dielectric layer 38 outside gaps 44 and 46, extends laterallyfrom thermal post 22 beyond and overlaps terminal 62, covers base 26outside the periphery of thermal post 22 in the upward direction, coversand surrounds thermal post 22 and signal post 24 in the lateraldirections, fills most of the space between substrate 34 and heatspreader 66 and is solidified.

Substrate 34 is mounted on and contacts adhesive 28, extends above theunderlying adhesive 28 and extends above base 26, conductive layer 36(as well as pad 56 and routing line 58) contacts and extends abovedielectric layer 38, and dielectric layer 38 contacts and is sandwichedbetween adhesive 28 and conductive layer 36.

Thermal post 22 and signal post 24 have the same thickness and arecoplanar with one another, and base 26 and terminal 62 have the samethickness and are coplanar with one another. Furthermore, posts 22 and24 are coplanar with adhesive 28 at both their tops and bottoms.

Thermal post 22, signal post 24, base 26, cap 60 and terminal 62 remainspaced from substrate 34. As a result, substrate 34 and heat spreader 66are mechanically attached and electrically isolated from one another.

Adhesive 28, dielectric layer 38 and solder masks 68 and 70 extend tostraight vertical peripheral edges of thermal board 74 after it isdetached or singulated from a batch of identical simultaneouslymanufactured thermal boards.

Pad 56 is customized as an electrical interface for a semiconductordevice such as an LED package or a semiconductor chip that issubsequently mounted on cap 60, terminal 62 is customized as anelectrical interface for the next level assembly such as a solderablewire from a printed circuit board, cap 60 is customized as a thermalinterface for the semiconductor device, and base 26 is customized as athermal interface for the next level assembly such as the printedcircuit board or a heat sink for an electronic device. Furthermore, cap60 is thermally connected to base 26 by thermal post 22.

Pad 56 and terminal 62 are vertically offset from one another andexposed at the top and bottom surfaces, respectively, of thermal board74, thereby providing vertical routing between the semiconductor deviceand the next level assembly.

Pad 56 and cap 60 are coplanar with one another at their top surfacesabove dielectric layer 38, and base 26 and terminal 62 are coplanar withone another at their bottom surfaces below adhesive 28.

Conductive trace 64 is shown in cross-section as a continuous circuittrace for convenience of illustration. However, conductive trace 64typically provides horizontal signal routing in both the X and Ydirections. That is, pad 56 and terminal 62 are laterally offset fromone another in the X and Y directions, and routing line 58 routes in theX and Y directions.

Heat spreader 66 provides heat spreading and heat dissipation from asemiconductor device that is subsequently mounted on cap 60 to the nextlevel assembly that thermal board 74 is subsequently mounted on. Thesemiconductor device generates heat that flows into cap 60, from cap 60into thermal post 22 and through thermal post 22 into base 26 where itis spread out and dissipated in the downward direction, for instance toan underlying heat sink.

Thermal board 74 does not expose thermal post 22, signal post 24 orrouting line 58. Thermal post 22 is covered by cap 60, signal post 24and routing line 58 are covered by solder mask 68, and adhesive 28 iscovered by solder masks 68 and 70. Thermal post 22, signal post 24,adhesive 28 and routing line 58 are shown in phantom in FIG. 4M forconvenience of illustration.

Thermal board 74 includes other conductive traces 64 that typicallyinclude signal post 24, pad 56, routing line 58 and terminal 62. Asingle conductive trace 64 is described and labeled for convenience ofillustration. In conductive traces 64, signal posts 24, pads 56 andterminals 62 generally have identical shapes and sizes whereas routinglines 58 generally have different routing configurations. For instance,some conductive traces 64 may be spaced and separated and electricallyisolated from one another whereas other conductive traces 64 canintersect or route to the same pad 56, routing line 58 or terminal 62and be electrically connected to one another. Likewise, some pads 56 mayreceive independent signals whereas other pads 56 share a common signal,power or ground.

Thermal board 74 can be adapted for an LED package with blue, green andred LED chips, with each LED chip including an anode and a cathode andeach LED package including a corresponding anode terminal and cathodeterminal. In this instance, thermal board 74 can include six pads 56 andfour terminals 62 so that each anode is routed from a separate pad 56 toa separate terminal 62 whereas each cathode is routed from a separatepad 56 to a common ground terminal 62.

A brief cleaning step can be applied to the structure at variousmanufacturing stages to remove oxides and debris that may be present onthe exposed metal. For instance, a brief oxygen plasma cleaning step canbe applied to the structure. Alternatively, a brief wet chemicalcleaning step using a solution containing potassium permanganate can beapplied to the structure. Likewise, the structure can be rinsed indistilled water to remove contaminants. The cleaning step cleans thedesired surfaces without appreciably affecting or damaging thestructure.

Advantageously, there is no plating bus or related circuitry that needbe disconnected or severed from conductive traces 64 after they areformed. A plating bus can be disconnected during the wet chemical etchthat forms pad 56, routing line 58, cap 60 and terminal 62.

Thermal board 74 can include registration holes (not shown) that aredrilled or sliced through adhesive 28, substrate 34 and solder masks 68and 70 so that thermal board 74 can be positioned by inserting toolingpins through the registration holes when it is subsequently mounted onan underlying carrier.

Thermal board 74 can omit cap 60. This can be accomplished by adjustingetch mask 52 to expose conductive layer 50 above all of aperture 40 tothe wet chemical etch that forms pad 56 and routing line 58. This canalso be accomplished by omitting conductive layer 50.

Thermal board 74 can accommodate multiple semiconductor devices ratherthan one. This can be accomplished by adjusting etch mask 16 to defineadditional thermal posts 22 and signal posts 24, adjusting adhesive 28to include additional openings 30 and 32, adjusting substrate 34 toinclude additional apertures 40 and 42, adjusting etch mask 52 to defineadditional pads 56, routing lines 58 and caps 60 and adjusting soldermask 68 to contain additional openings. The elements except forterminals 62 can be laterally repositioned to provide a 2×2 array forfour semiconductor devices. In addition, the topography (lateral shape)can be adjusted for some but not all of the elements. For instance, pads56, caps 60 and terminals 62 can retain the same topography whereasrouting lines 58 have different routing configurations.

FIGS. 5A, 5B and 5C are cross-sectional, top and bottom views,respectively, of a thermal board with a conductive trace on an adhesivein accordance with an embodiment of the present invention.

In this embodiment, the conductive trace contacts the adhesive and thedielectric layer is omitted. For purposes of brevity, any description ofthermal board 74 is incorporated herein insofar as the same isapplicable, and the same description need not be repeated. Likewise,elements of the thermal board similar to those in thermal board 74 havecorresponding reference numerals.

Thermal board 76 includes adhesive 28, conductive trace 64, heatspreader 66 and solder masks 68 and 70. Conductive trace 64 includessignal post 24, pad 56, routing line 58 and terminal 62. Heat spreader66 includes thermal post 22, base 26 and cap 60.

Conductive layer 36 is thicker in this embodiment than the previousembodiment. For instance, conductive layer 36 has a thickness of 130microns (rather than 30 microns) so that it can be handled withoutwarping or wobbling. Pad 56 and routing line 58 are therefore thickerand contact and overlap adhesive 28, and thermal board 76 is devoid of adielectric layer corresponding to dielectric layer 38.

Thermal board 76 can be manufactured in a manner similar to thermalboard 74 with suitable adjustments for thermal post 22, signal post 24and conductive layer 36. For instance, metal plate 10 has a thickness of280 microns (rather than 330 microns) so that posts 22 and 24 have aheight of 250 microns (rather than 300 microns). This can beaccomplished by reducing the etch time. Thereafter, adhesive 28 ismounted on base 26, conductive layer 36 alone is mounted on adhesive 28,heat and pressure are applied to flow and solidify adhesive 28, grindingis applied to planarize the top surface and then conductive layer 50 isdeposited on the top surface as previously described. Thereafter,conductive layers 36 and 50 are etched to form pad 56 and routing line58, conductive layer 50 is etched to form cap 60 and base 26 is etchedto form terminal 62, then solder mask 68 is formed on the top surface toselectively expose pad 56 and cap 60 and solder mask 70 is formed on thebottom surface to selectively expose base 26 and terminal 62 and thenplated contacts 72 provide a surface finish for base 26, pad 56, cap 60and terminal 62.

FIGS. 6A, 6B and 6C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard an LED package with backside contacts in accordance with anembodiment of the present invention.

Semiconductor chip assembly 100 includes thermal board 74, LED package102 and solder joints 104 and 106. LED package 102 includes LED chip108, submount 110, wire bond 112, electrical contact 114, thermalcontact 116 and transparent encapsulant 118. LED chip 108 includes anelectrode (not shown) electrically connected to a via (not shown) insubmount 110 by wire bond 112, thereby electrically connecting LED chip108 to electrical contact 114. LED chip 108 is mounted on and thermallyconnected to and mechanically attached to submount 110 by a die attach(not shown), thereby thermally connecting LED chip 108 to thermalcontact 116. Submount 110 is a ceramic block with low electricalconductivity and high thermal conductivity, and contacts 114 and 116 areplated on and protrude downwardly from the backside of submount 110.

LED package 102 is mounted on substrate 34 and heat spreader 66,electrically connected to substrate 34 and thermally connected to heatspreader 66. In particular, LED package 102 is mounted on pad 56 and cap60, overlaps thermal post 22, is electrically connected to substrate 34by solder joint 104 and is thermally connected to heat spreader 66 bysolder joint 106. For instance, solder joint 104 contacts and issandwiched between and electrically connects and mechanically attachespad 56 and electrical contact 114, thereby electrically connecting LEDchip 108 to terminal 62. Likewise, solder joint 106 contacts and issandwiched between and thermally connects and mechanically attaches cap60 and thermal contact 116, thereby thermally connecting LED chip 108 tobase 26. Pad 56 is spot plated with nickel/gold to bond well with solderjoint 104 and is shaped and sized to match electrical contact 114,thereby improving signal transfer from substrate 34 to LED package 102.Likewise, cap 60 is spot plated with nickel/gold to bond well withsolder joint 106 and is shaped and sized to match thermal contact 116,thereby improving heat transfer from LED package 102 to heat spreader66. Furthermore, thermal post 22 is not and need not be shaped and sizedto match thermal contact 116.

Transparent encapsulant 118 is a solid adherent electrically insulativeprotective plastic enclosure that provides environmental protection suchas moisture resistance and particle protection for LED chip 108 and wirebond 112. LED chip 108 and wire bond 112 are embedded in transparentencapsulant 118.

Semiconductor chip assembly 100 can be manufactured by depositing asolder material on pad 56 and cap 60, then placing contacts 114 and 116on the solder material over pad 56 and cap 60, respectively, and thenreflowing the solder material to provide solder joints 104 and 106.

For instance, solder paste is selectively screen printed on pad 56 andcap 60, then LED package 102 is positioned over thermal board 74 using apick-up head and an automated pattern recognition system instep-and-repeat fashion. The pick-up head places contacts 114 and 116 onthe solder paste over pad 56 and cap 60, respectively. Next, the solderpaste is heated and reflowed at a relatively low temperature such as190° C. and then the heat is removed and the solder paste cools andsolidifies to form hardened solder joints 104 and 106. Alternatively,solder balls are placed on pad 56 and cap 60, then contacts 114 and 116are placed on the solder balls over pad 56 and cap 60, respectively, andthen the solder balls are heated and reflowed to form solder joints 104and 106.

The solder material can be initially deposited on thermal board 74 orLED package 102 by plating or printing or placement techniques, thensandwiched between thermal board 74 and LED package 102 and thenreflowed. The solder material can also be deposited on terminal 62 ifrequired for the next level assembly. Furthermore, a conductive adhesivesuch as silver-filled epoxy or other connection media can be usedinstead of solder, and the connection media on pad 56, cap 60 andterminal 62 need not be the same.

Semiconductor chip assembly 100 is a second-level single-chip module.

FIGS. 7A, 7B and 7C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard and an LED package with lateral leads in accordance with anembodiment of the present invention.

In this embodiment, the LED package has lateral leads rather thanbackside contacts. For purposes of brevity, any description of assembly100 is incorporated herein insofar as the same is applicable, and thesame description need not be repeated. Likewise, elements of theassembly similar to those in assembly 100 have corresponding referencenumerals indexed at two-hundred rather than one-hundred. For instance,LED chip 208 corresponds to LED chip 108, submount 210 corresponds tosubmount 110, etc.

Semiconductor chip assembly 200 includes thermal board 74, LED package202 and solder joints 204 and 206. LED package 202 includes LED chip208, submount 210, wire bond 212, lead 214 and transparent encapsulant218. LED chip 208 is electrically connected to lead 214 by wire bond212. Submount 210 includes thermal contact surface 216 at its backside,is narrower than submount 110 and has the same lateral size and shape asthermal contact 116. LED chip 208 is mounted on and thermally connectedto and mechanically attached to submount 210 by a die attach (notshown), thereby thermally connecting LED chip 208 to thermal contactsurface 216. Lead 214 extends laterally from submount 210 and thermalcontact surface 216 faces downward.

LED package 202 is mounted on substrate 34 and heat spreader 66,electrically connected to substrate 34 and thermally connected to heatspreader 66. In particular, LED package 202 is mounted on pad 56 and cap60, overlaps thermal post 22, is electrically connected to substrate 34by solder joint 204 and is thermally connected to heat spreader 66 bysolder joint 206. For instance, solder joint 204 contacts and issandwiched between and electrically connects and mechanically attachespad 56 and lead 214, thereby electrically connecting LED chip 208 toterminal 62. Likewise, solder joint 206 contacts and is sandwichedbetween and thermally connects and mechanically attaches cap 60 andthermal contact surface 216, thereby thermally connecting LED chip 208to base 26.

Semiconductor chip assembly 200 can be manufactured by depositing asolder material on pad 56 and cap 60, then placing lead 214 and thermalcontact surface 216 on the solder material over pad 56 and cap 60,respectively, and then reflowing the solder material to provide solderjoints 204 and 206.

Semiconductor chip assembly 200 is a second-level single-chip module.

FIGS. 8A, 8B and 8C are cross-sectional, top and bottom views,respectively, of a semiconductor chip assembly that includes a thermalboard and a semiconductor chip in accordance with an embodiment of thepresent invention.

In this embodiment, the semiconductor device is a chip rather than apackage and the chip is mounted on the heat spreader but not thesubstrate. Furthermore, the chip overlaps the thermal post but not thesubstrate, is electrically connected to the pad using a wire bond and isthermally connected to the cap using a die attach.

Semiconductor chip assembly 300 includes thermal board 74, chip 302,wire bond 304, die attach 306 and encapsulant 308. Chip 302 includes topsurface 310, bottom surface 312 and bond pad 314. Top surface 310 is theactive surface and includes bond pad 314 and bottom surface 312 is thethermal contact surface.

Chip 302 is mounted on heat spreader 66, electrically connected tosubstrate 34 and thermally connected to heat spreader 66. In particular,chip 302 is mounted on cap 60, is within the periphery of cap 60,overlaps thermal post 22 but does not overlap substrate 34, iselectrically connected to substrate 34 by wire bond 304 and is thermallyconnected to and mechanically attached to heat spreader 66 by die attach306. For instance, wire bond 304 is bonded to and electrically connectspads 56 and 314, thereby electrically connecting chip 302 to terminal62. Likewise, die attach 306 contacts and is sandwiched between andthermally connects and mechanically attaches cap 60 and thermal contactsurface 312, thereby thermally connecting chip 302 to base 26. Pad 56 isspot plated with nickel/silver to bond well with wire bond 304, therebyimproving signal transfer from substrate 34 to chip 302, and cap 60 isshaped and sized to match thermal contact surface 312, thereby improvingheat transfer from chip 302 to heat spreader 66. Furthermore, thermalpost 22 is not and need not be shaped and sized to match thermal contactsurface 312.

Encapsulant 308 is a solid adherent electrically insulative protectiveplastic enclosure that provides environmental protection such asmoisture resistance and particle protection for chip 302 and wire bond304. Chip 302 and wire bond 304 are embedded in encapsulant 308.Furthermore, encapsulant 308 can be transparent if chip 302 is anoptical chip such as an LED. Encapsulant 308 is transparent in FIG. 8Bfor convenience of illustration.

Semiconductor chip assembly 300 can be manufactured by mounting chip 302on cap 60 using die attach 306, then wire bonding pads 56 and 314 andthen forming encapsulant 308.

For instance, die attach 306 is initially a silver-filled epoxy pastewith high thermal conductivity that is selectively screen printed on cap60 and then chip 302 placed on the epoxy paste using a pick-up head andan automated pattern recognition system in step-and-repeat fashion.Thereafter, the epoxy paste is heated and hardened at a relatively lowtemperature such as 190° C. to form die attach 306. Next, wire bond 304is a gold wire that is thermosonically ball bonded to pads 56 and 314and then encapsulant 308 is transfer molded on the structure.

Chip 302 can be electrically connected to pad 56 by a wide variety ofconnection media, thermally connected to and mechanically attached toheat spreader 66 by a wide variety of thermal adhesives and encapsulatedby a wide variety of encapsulants.

Semiconductor chip assembly 300 is a first-level single-chip package.

The semiconductor chip assemblies and thermal boards described above aremerely exemplary. Numerous other embodiments are contemplated. Inaddition, the embodiments described above can be mixed-and-matched withone another and with other embodiments depending on design andreliability considerations. For instance, the substrate can includesingle-level conductive traces and multi-level conductive traces. Thethermal board can include multiple posts arranged in an array formultiple semiconductor devices and can include additional conductivetraces to accommodate the additional semiconductor devices. Likewise,the semiconductor device can be an LED package with multiple LED chipsand the thermal board can include additional conductive traces toaccommodate the additional LED chips. The semiconductor device and thecap can overlap the substrate and cover the thermal post in the upwarddirection.

The semiconductor device can share or not share the heat spreader withother semiconductor devices. For instance, a single semiconductor devicecan be mounted on the heat spreader. Alternatively, numeroussemiconductor devices can mounted on the heat spreader. For instance,four small chips in a 2×2 array can be attached to the thermal post andthe substrate can include additional conductive traces to receive androute additional wire bonds to the chips. This may be more costeffective than providing a miniature thermal post for each chip.

The semiconductor chip can be optical or non-optical. For instance, thechip can be an LED, a solar cell, a microprocessor, a controller or anRF power amplifier. Likewise, the semiconductor package can be an LEDpackage or an RF module. Thus, the semiconductor device can be apackaged or unpackaged optical or non-optical chip. Furthermore, thesemiconductor device can be mechanically, electrically and thermallyconnected to the thermal board using a wide variety of connection mediaincluding solder and electrically and/or thermally conductive adhesive.

The heat spreader can provide rapid, efficient and essentially uniformheat spreading and dissipation for the semiconductor device to the nextlevel assembly without heat flow through the adhesive, the substrate orelsewhere in the thermal board. As a result, the adhesive can have lowthermal conductivity which drastically reduces cost. The heat spreadercan include a thermal post and base that are integral with one anotherand a cap that is metallurgically bonded and thermally connected to thethermal post, thereby enhancing reliability and reducing cost. The capcan be coplanar with the pad, thereby facilitating the electrical,thermal and mechanical connections with the semiconductor device.Furthermore, the cap can be customized for the semiconductor device andthe base can be customized for the next level assembly, therebyenhancing the thermal connection from the semiconductor device to thenext level assembly. For instance, the thermal post can have a circularshape in a lateral plane and the cap can have a square or rectangularshape in a lateral plane with the same or similar topography as thethermal contact of the semiconductor device.

The heat spreader can be electrically connected to or isolated from thesemiconductor device and the substrate. For instance, the secondconductive layer on the grinded surface can include a routing line thatextends across the adhesive between the substrate and the cap andelectrically connects the semiconductor device to the heat spreader.Thereafter, the heat spreader can be electrically connected to ground,thereby electrically connecting the semiconductor device to ground.

The heat spreader can be copper, aluminum, copper/nickel/aluminum orother thermally conductive metallic structures.

The thermal post can be deposited on or integral with the base. Thethermal post can be integral with the base when the they are asingle-piece metal such as copper or aluminum. The thermal post can alsobe integral with the base when they include a single-piece metal such ascopper at their interface as well as additional metal elsewhere such asa solder upper post portion and a copper lower post portion and base.The thermal post can also be integral with the base when they sharesingle-piece metals at their interface such as a copper coating on anickel buffer layer on an aluminum core.

The signal post can be deposited on or integral with the terminal. Thesignal post can be integral with the terminal when the they are asingle-piece metal such as copper or aluminum. The signal post can alsobe integral with the terminal when they include a single-piece metalsuch as copper at their interface as well as additional metal elsewheresuch as a solder upper post portion and a copper lower post portion andterminal. The signal post can also be integral with the terminal whenthey share single-piece metals at their interface such as a coppercoating on a nickel buffer layer on an aluminum core.

The thermal post can include a flat top surface that is coplanar withthe adhesive. For instance, the thermal post can be coplanar with theadhesive or the thermal post can be etched after the adhesive issolidified to provide a cavity in the adhesive over the thermal post.The thermal post can also be selectively etched to provide a cavity inthe thermal post that extends below its top surface. In any case, thesemiconductor device can be mounted on the thermal post and located inthe cavity, and the wire bond can extend from the semiconductor devicein the cavity to the pad outside the cavity. In this instance, thesemiconductor device can be an LED chip and the cavity can focus the LEDlight in the upward direction.

The base can provide mechanical support for the substrate. For instance,the base can prevent the substrate from warping during metal grinding,chip mounting, wire bonding and encapsulant molding. Furthermore, thebase can include fins at its backside that protrude in the downwarddirection. For instance, the base can be cut at its bottom surface by arouting machine to form lateral grooves that define the fins. In thisinstance, the base can have a thickness of 500 microns, the grooves canhave a depth of 300 microns and the fins can have a height of 300microns. The fins can increase the surface area of the base, therebyincreasing the thermal conductivity of the base by thermal convectionwhen it remains exposed to the air rather than mounted on a heat sink.

The cap can be formed by numerous deposition techniques includingelectroplating, electroless plating, evaporating and sputtering as asingle layer or multiple layers after the adhesive is solidified, eitherbefore, during or after the pad and/or the terminal is formed. The capcan be the same metal as the thermal post or the adjacent top of thethermal post. Furthermore, the cap can extend across the aperture to thesubstrate or reside within the periphery of the aperture. Thus, the capmay contact or be spaced from the substrate. In any case, the capextends laterally from the top of the thermal post in the lateraldirections.

The adhesive can provide a robust mechanical bond between the heatspreader and the substrate. For instance, the adhesive can extendlaterally from the thermal post beyond the conductive trace to theperipheral edges of the assembly, the adhesive can fill the spacebetween the heat spreader and the substrate and the adhesive can bevoid-free with consistent bond lines. The adhesive can also absorbthermal expansion mismatch between the heat spreader and the substrate.Furthermore, the adhesive can be a low cost dielectric that need nothave high thermal conductivity. Moreover, the adhesive is not prone todelamination.

The adhesive thickness can be adjusted so that the adhesive essentiallyfills the gaps and essentially all the adhesive is within structure onceit is solidified and/or grinded. For instance, the optimal prepregthickness can be established through trial and error. Likewise, thedielectric layer thickness can be adjusted to achieve this result.

The substrate can be a low cost laminated structure that need not havehigh thermal conductivity. Furthermore, the substrate can include asingle conductive layer or multiple conductive layers. Moreover, thesubstrate can include or consist of the conductive layer.

The conductive layer alone can be mounted on the adhesive. For instance,the apertures can be formed in the conductive layer and then theconductive layer can be mounted on the adhesive so that the conductivelayer contacts the adhesive and is exposed in the upward direction andthe posts extend into and are exposed in the upward direction by theapertures. In this instance, the conductive layer can have a thicknessof 100 to 200 microns such as 125 microns which is thick enough tohandle without warping and wobbling yet thin enough to pattern withoutexcessive etching.

The conductive layer and the dielectric layer can be mounted on theadhesive. For instance, the conductive layer can be provided on thedielectric layer, then the apertures can be formed in the conductivelayer and the dielectric layer, and then the conductive layer and thedielectric layer can be mounted on the adhesive so that the conductivelayer is exposed in the upward direction, the dielectric layer contactsand is sandwiched between and separates the conductive layer and theadhesive and the posts extend into and are exposed in the upwarddirections by the apertures. In this instance, the conductive layer canhave a thickness of 10 to 50 microns such as 30 microns which is thickenough for reliable signal transfer yet thin enough to reduce weight andcost. Furthermore, the dielectric layer is a permanent part of thethermal board.

The conductive layer and a carrier can be mounted on the adhesive. Forinstance, the conductive layer can be attached to a carrier suchbiaxially-oriented polyethylene terephthalate polyester (Mylar) by athin film, then the apertures can be formed in the conductive layer butnot the carrier, then the conductive layer and the carrier can bemounted on the adhesive so that the carrier covers the conductive layerand is exposed in the upward direction, the thin film contacts and issandwiched between the carrier and the conductive layer, the conductivelayer contacts and is sandwiched between the thin film and the adhesive,and the posts are aligned with the apertures and covered in the upwarddirection by the carrier. After the adhesive is solidified, the thinfilm can be decomposed by UV light so that the carrier can be peeled offthe conductive layer, thereby exposing the conductive layer in theupward direction, and then the conductive layer can be grinded andpatterned to provide the conductive trace. In this instance, theconductive layer can have a thickness of 10 to 50 microns such as 30microns which is thick enough for reliable signal transfer yet thinenough to reduce weight and cost, and the carrier can have a thicknessof 300 to 500 microns which is thick enough to handle without warpingand wobbling yet thin enough to reduce weight and cost. Furthermore, thecarrier is a temporary fixture and not a permanent part of the thermalboard.

The pad and the terminal can have a wide variety of packaging formats asrequired by the semiconductor device and the next level assembly.

The pad and the cap can be coplanar at their top surfaces, therebyenhancing solder joints between the semiconductor device and the thermalboard by controlling solder ball collapse.

The pad and the routing line over the dielectric layer can be formed bynumerous deposition techniques including electroplating, electrolessplating, evaporating and sputtering as a single layer or multiplelayers, either before or after the substrate is mounted on the adhesive.For instance, the conductive layer can be patterned on the substratebefore it is mounted on the adhesive or after it is attached to theposts and the base by the adhesive.

The plated contact surface finish can be formed before or after the padand the terminal are formed. For instance, the plated layer can bedeposited on the base and the second conductive layer and then patternedusing the etch masks that define the pad and the terminal.

The conductive trace can include additional pads, terminals, vias,signal posts and routing lines as well as passive components and havedifferent configurations. The conductive trace can function as a signal,power or ground layer depending on the purpose of the correspondingsemiconductor device pad. The conductive trace can also include variousconductive metals such as copper, gold, nickel, silver, palladium, tin,combinations thereof, and alloys thereof. The preferred composition willdepend on the nature of the external connection media as well as designand reliability considerations. Furthermore, those skilled in the artwill understand that in the context of a semiconductor chip assembly,the copper material can be pure elemental copper but is typically acopper alloy that is mostly copper such as copper-zirconium (99.9%copper), copper-silver-phosphorus-magnesium (99.7% copper) andcopper-tin-iron-phosphorus (99.7% copper) to improve mechanicalproperties such as tensile strength and elongation.

The cap, dielectric layer, solder masks, plated contacts and secondconductive layer on the grinded surface are generally desirable but maybe omitted in some embodiments. For instance, if the opening andaperture are punched rather than drilled so that the top of the thermalpost is shaped and sized to accommodate a thermal contact surface of thesemiconductor device then the cap and the second conductive layer may beomitted to reduce cost. Likewise, the dielectric layer may be omitted toreduce cost.

The thermal board can include a thermal via that is spaced from theposts, extends through the dielectric layer and the adhesive outside theopenings and the apertures and is adjacent to and thermally connects thebase and the cap to improve heat dissipation from the cap to the baseand heat spreading in the base.

The assembly can provide horizontal or vertical single-level ormulti-level signal routing.

Horizontal single-level signal routing with the pad, the terminal andthe routing line above the dielectric layer is disclosed in U.S.application Ser. No. 12/616,773 filed Nov. 11, 2009 by Charles W. C. Linet al. entitled “Semiconductor Chip Assembly with Post/Base HeatSpreader and Substrate” which is incorporated by reference.

Horizontal single-level signal routing with the pad, the terminal andthe routing line above the adhesive and no dielectric layer is disclosedin U.S. application Ser. No. 12/616,775 filed Nov. 11, 2009 by CharlesW. C. Lin et al. entitled “Semiconductor Chip Assembly with Post/BaseHeat Spreader and Conductive Trace” which is incorporated by reference.

Horizontal multi-level signal routing with the pad and the terminalabove the dielectric layer electrically connected by first and secondvias through the dielectric layer and a routing line beneath thedielectric layer is disclosed in U.S. application Ser. No. 12/557,540filed Sep. 11, 2009 by Chia-Chung Wang et al. entitled “SemiconductorChip Assembly with Post/Base Heat Spreader and Horizontal SignalRouting” which is incorporated by reference.

Vertical multi-level signal routing with the pad above the dielectriclayer and the terminal beneath the adhesive electrically connected by afirst via through the dielectric layer, a routing line beneath thedielectric layer and a second via through the adhesive is disclosed inU.S. application Ser. No. 12/557,541 filed Sep. 11, 2009 by Chia-ChungWang et al. entitled “Semiconductor Chip Assembly with Post/Base HeatSpreader and Vertical Signal Routing” which is incorporated byreference.

The working format for the thermal board can be a single thermal boardor multiple thermal boards based on the manufacturing design. Forinstance, a single thermal board can be manufactured individually.Alternatively, numerous thermal boards can be simultaneously batchmanufactured using a single metal plate, a single adhesive, a singlesubstrate and a single top and bottom solder mask and then separatedfrom one another. Likewise, numerous sets of heat spreaders andconductive traces that are each dedicated to a single semiconductordevice can be simultaneously batch manufactured for each thermal boardin the batch using a single metal plate, a single adhesive, a singlesubstrate and a single top and bottom solder mask.

For example, multiple recesses can be etched in the metal plate to formmultiple thermal posts and signal posts and the base, then thenon-solidified adhesive with openings corresponding to the posts can bemounted on the base such that each post extends through an opening, thenthe substrate (with a single conductive layer, a single dielectric layerand apertures corresponding to the posts) can be mounted on the adhesivesuch that each post extends through an opening into an aperture, thenthe base and the substrate can be moved towards one another by platensto force the adhesive into the gaps in the apertures between the postsand the substrate, then the adhesive can be cured and solidified, thenthe posts, the adhesive and the first conductive layer can be grinded toform a lateral top surface, then the second conductive layer can beplated on the posts, the adhesive and the first conductive layer, thenthe first and second conductive layers can be etched to form the padsand the routing lines corresponding to the signal posts, the secondconductive layer can be etched to form the caps corresponding to thethermal posts and the base can be etched to form the bases correspondingto the thermal posts and the terminals corresponding to the signalposts, then the top solder mask can be deposited on the structure andpatterned to expose the pads and the caps and the bottom solder mask canbe deposited on the structure and patterned to expose the bases and theterminals, then the plated contact surface finish can be formed on thebases, the pads, the terminals and the caps and then the substrate, theadhesive and the solder masks can be cut or cracked at the desiredlocations of the peripheral edges of the thermal boards, therebyseparating the individual thermal boards from one another.

The working format for the semiconductor chip assembly can be a singleassembly or multiple assemblies based on the manufacturing design. Forinstance, a single assembly can be manufactured individually.Alternatively, numerous assemblies can be simultaneously batchmanufactured before the thermal boards are separated from one another.Likewise, multiple semiconductor devices can be electrically, thermallyand mechanically connected to each thermal board in the batch.

For example, solder paste portions can be deposited on the pads and thecaps, then the LED packages can be placed on the solder paste portions,then the solder paste portions can be simultaneously heated, reflowedand hardened to provide the solder joints, and then the thermal boardscan be separated from one another.

As another example, die attach paste portions can be deposited on thecaps, then the chips can be placed on the die attach paste portions,then the die attach paste portions can be simultaneously heated andhardened to provide the die attaches, then the chips can be wired bondedto the corresponding pads, then the encapsulant can be formed over thechips and the wire bonds, and then the thermal boards can be separatedfrom one another.

The thermal boards can be detached from one another in a single step ormultiple steps. For instance, the thermal boards can be batchmanufactured as a panel, then the semiconductor devices can be mountedon the panel and then the semiconductor chip assemblies of the panel canbe detached from one another. Alternatively, the thermal boards can bebatch manufactured as a panel, then the thermal boards of the panel canbe singulated into strips of multiple thermal boards, then thesemiconductor devices can be mounted on the thermal boards of a stripand then the semiconductor chip assemblies of the strip can be detachedfrom one another. Furthermore, the thermal boards can be detached bymechanical sawing, laser sawing, cleaving or other suitable techniques.

The term “adjacent” refers to elements that are integral (single-piece)or in contact (not spaced or separated from) with one another. Forinstance, the thermal post is adjacent to the base regardless of whetherthe thermal post is formed additively or subtractively.

The term “overlap” refers to above and extending within a periphery ofan underlying element. Overlap includes extending inside and outside theperiphery or residing within the periphery. For instance, thesemiconductor device overlaps the thermal post since an imaginaryvertical line intersects the semiconductor device and the thermal post,regardless of whether another element such as the cap is between thesemiconductor device and the thermal post and is intersected by theline, and regardless of whether another imaginary vertical lineintersects the semiconductor device but not the thermal post (outsidethe periphery of the thermal post). Likewise, the adhesive overlaps thebase and is overlapped by the pad, and the base is overlapped by thethermal post. Likewise, the thermal post overlaps and is within aperiphery of the base. Moreover, overlap is synonymous with over andoverlapped by is synonymous with under or beneath.

The term “contact” refers to direct contact. For instance, thedielectric layer contacts the pad but does not contact the thermal postor the base.

The term “cover” refers to complete coverage in the upward, downwardand/or lateral directions. For instance, the base covers the thermalpost in the downward direction but the thermal post does not cover thebase in the upward direction.

The term “layer” refers to patterned and unpatterned layers. Forinstance, the conductive layer can be an unpatterned blanket sheet onthe dielectric layer when the substrate is mounted on the adhesive, andthe conductive layer can be a patterned circuit with spaced traces onthe dielectric layer when the semiconductor device is mounted on theheat spreader. Furthermore, a layer can include stacked layers.

The term “pad” in conjunction with the conductive trace refers to aconnection region that is adapted to contact and/or bond to externalconnection media (such as solder or a wire bond) that electricallyconnects the conductive trace to the semiconductor device.

The term “terminal” in conjunction with the conductive trace refers to aconnection region that is adapted to contact and/or bond to externalconnection media (such as solder or a wire bond) that electricallyconnects the conductive trace to an external device (such as a PCB or awire thereto) associated with the next level assembly.

The term “cap” in conjunction with the heat spreader refers to a contactregion that is adapted to contact and/or bond to external connectionmedia (such as solder or thermally conductive adhesive) that thermallyconnects the heat spreader to the semiconductor device.

The terms “opening” and “aperture” refer to a through-hole and aresynonymous. For instance, the thermal post is exposed by the adhesive inthe upward direction when it is inserted into the opening in theadhesive. Likewise, the thermal post is exposed by the substrate in theupward direction when it is inserted into the aperture in the substrate.

The term “inserted” refers to relative motion between elements. Forinstance, the thermal post is inserted into the aperture regardless ofwhether the thermal post is stationary and the substrate moves towardsthe base, the substrate is stationary and the thermal post moves towardsthe substrate or the thermal post and the substrate both approach theother. Furthermore, the thermal post is inserted (or extends) into theaperture regardless of whether it goes through (enters and exits) ordoes not go through (enters without exiting) the aperture.

The phrase “move towards one another” also refers to relative motionbetween elements. For instance, the base and the substrate move towardsone another regardless of whether the base is stationary and thesubstrate moves towards the base, the substrate is stationary and thebase moves towards the substrate or the base and the substrate bothapproach the other.

The phrase “aligned with” refers to relative position between elements.For instance, the thermal post is aligned with the aperture when theadhesive is mounted on the base, the substrate is mounted on theadhesive, the thermal post is inserted into and aligned with the openingand the aperture is aligned with the opening regardless of whether thethermal post is inserted into the aperture or is below and spaced fromthe aperture.

The phrase “mounted on” includes contact and non-contact with a singleor multiple support element(s). For instance, the semiconductor deviceis mounted on the heat spreader regardless of whether it contacts theheat spreader or is separated from the heat spreader by a die attach.Likewise, the semiconductor device is mounted on the heat spreaderregardless of whether it is mounted on the heat spreader alone or theheat spreader and the substrate.

The phrase “adhesive . . . in the gap” refers to the adhesive in thegap. For instance, adhesive that extends across the dielectric layer inthe gap refers to the adhesive in the gap that extends across thedielectric layer. Likewise, adhesive that contacts and is sandwichedbetween the thermal post and the dielectric layer in the gap refers tothe adhesive in the gap that contacts and is sandwiched between thethermal post at the inner sidewall of the gap and the dielectric layerat the outer sidewall of the gap.

The term “above” refers to upward extension and includes adjacent andnon-adjacent elements as well as overlapping and non-overlappingelements. For instance, the thermal post extends above, is adjacent to,overlaps and protrudes from the base. Likewise, the thermal post extendsabove the dielectric layer even though it is not adjacent to or overlapthe dielectric layer.

The term “below” refers to downward extension and includes adjacent andnon-adjacent elements as well as overlapping and non-overlappingelements. For instance, the base extends below, is adjacent to, isoverlapped by and protrudes from the thermal post. Likewise, the thermalpost extends below the dielectric layer even though it is not adjacentto or overlapped by the dielectric layer.

The “upward” and “downward” vertical directions do not depend on theorientation of the semiconductor chip assembly (or the thermal board),as will be readily apparent to those skilled in the art. For instance,the thermal post extends vertically above the base in the upwarddirection and the adhesive extends vertically below the pad in thedownward direction regardless of whether the assembly is inverted and/ormounted on a heat sink. Likewise, the base extends “laterally” from thethermal post in a lateral plane regardless of whether the assembly isinverted, rotated or slanted. Thus, the upward and downward directionsare opposite one another and orthogonal to the lateral directions, andlaterally aligned elements are coplanar with one another at a lateralplane orthogonal to the upward and downward directions.

The semiconductor chip assembly of the present invention has numerousadvantages. The assembly is reliable, inexpensive and well-suited forhigh volume manufacture. The assembly is especially well-suited for highpower semiconductor devices such as LED packages and large semiconductorchips as well as multiple semiconductor devices such as smallsemiconductor chips in arrays which generate considerable heat andrequire excellent heat dissipation in order to operate effectively andreliably.

The manufacturing process is highly versatile and permits a wide varietyof mature electrical, thermal and mechanical connection technologies tobe used in a unique and improved manner. The manufacturing process canalso be performed without expensive tooling. As a result, themanufacturing process significantly enhances throughput, yield,performance and cost effectiveness compared to conventional packagingtechniques. Moreover, the assembly is well-suited for copper chip andlead-free environmental requirements.

The embodiments described herein are exemplary and may simplify or omitelements or steps well-known to those skilled in the art to preventobscuring the present invention. Likewise, the drawings may omitduplicative or unnecessary elements and reference labels to improveclarity.

Various changes and modifications to the embodiments described hereinwill be apparent to those skilled in the art. For instance, thematerials, dimensions, shapes, sizes, steps and arrangement of stepsdescribed above are merely exemplary. Such changes, modifications andequivalents may be made without departing from the spirit and scope ofthe present invention as defined in the appended claims.

1. A semiconductor chip assembly, comprising: a semiconductor device; anadhesive that includes first and second openings; a heat spreader thatincludes a thermal post and a base, wherein the thermal post is adjacentto the base and extends above the base in an upward direction, and thebase extends below the thermal post in a downward direction opposite theupward direction and extends laterally from the thermal post in lateraldirections orthogonal to the upward and downward directions; and aconductive trace that includes a pad, a terminal and a signal post,wherein the signal post extends below the pad and above the terminal andan electrically conductive path between the pad and the terminalincludes the signal post; wherein the semiconductor device is above andoverlaps the thermal post, is electrically connected to the pad andthereby electrically connected to the terminal, and is thermallyconnected to the thermal post and thereby thermally connected to thebase; wherein the adhesive is mounted on and extends above the base andextends laterally from the thermal post to or beyond the terminal;wherein the pad extends above the adhesive and the terminal extendsbelow the adhesive; and wherein the thermal post extends into the firstopening, the signal post extends into the second opening, the posts havethe same thickness and are coplanar with one another, and the base andthe terminal have the same thickness and are coplanar with one another.2. The assembly of claim 1, wherein the semiconductor device is an LEDpackage that includes an LED chip.
 3. The assembly of claim 2, whereinthe LED package is electrically connected to the pad using a firstsolder joint and is thermally connected to the heat spreader using asecond solder joint.
 4. The assembly of claim 1, wherein thesemiconductor device is a semiconductor chip.
 5. The assembly of claim4, wherein the chip is electrically connected to the pad using a wirebond and is thermally connected to the heat spreader using a die attach.6. The assembly of claim 1, wherein the adhesive contacts the posts, thebase, the pad and the terminal.
 7. The assembly of claim 1, wherein theadhesive covers and surrounds the posts in the lateral directions. 8.The assembly of claim 1, wherein the adhesive conformally coatssidewalls of the posts.
 9. The assembly of claim 1, wherein the adhesiveis coplanar with tops and bottoms of the posts.
 10. The assembly ofclaim 1, wherein the adhesive extends laterally from the thermal postbeyond the terminal.
 11. The assembly of claim 1, wherein the adhesiveextends to peripheral edges of the assembly.
 12. The assembly of claim1, wherein the thermal post is integral with the base and the signalpost is integral with the terminal.
 13. The assembly of claim 1, whereinthe thermal post has a cut-off conical shape in which its diameterdecreases as it extends upwardly from the base to its flat top, and thesignal post has a cut-off conical shape in which its diameter decreasesas it extends upwardly from the terminal to its flat top.
 14. Theassembly of claim 1, wherein the base covers the thermal post in thedownward direction, supports the adhesive and is spaced from peripheraledges of the assembly.
 15. The assembly of claim 1, wherein theconductive trace is spaced from the heat spreader and the pad, theterminal and the signal post contact the adhesive.
 16. The assembly ofclaim 1, wherein the terminal is adjacent to and extends below thesignal post and extends laterally from the signal post in the lateraldirections.
 17. The assembly of claim 1, wherein the heat spreaderincludes a cap that is above and adjacent to and covers in the upwarddirection and extends laterally in the lateral directions from the topof the thermal post.
 18. The assembly of claim 17, wherein the cap iscoplanar with the pad above the adhesive.
 19. The assembly of claim 17,wherein the cap has a rectangular or square shape and the top of thethermal post has a circular shape.
 20. The assembly of claim 17, whereinthe cap is sized and shaped to accommodate a thermal contact surface ofthe semiconductor device, and the top of the thermal post is not sizedand shaped to accommodate the thermal contact surface of thesemiconductor device.
 21. A semiconductor chip assembly, comprising: asemiconductor device; an adhesive that includes first and secondopenings; a heat spreader that includes a thermal post and a base,wherein the thermal post is adjacent to and integral with the base andextends above the base in an upward direction, the base extends belowthe thermal post in a downward direction opposite the upward directionand extends laterally from the thermal post in lateral directionsorthogonal to the upward and downward directions; and a conductive tracethat includes a pad, a terminal, a routing line and a signal post,wherein the routing line is adjacent to pad, the signal post is adjacentto the routing line and the terminal, extends below the pad and therouting line and extends above the terminal, and an electricallyconductive path between the pad and the terminal includes the routingline and the signal post; wherein the semiconductor device is mounted onthe heat spreader, overlaps the thermal post, does not overlap thesignal post, is electrically connected to the pad and therebyelectrically connected to the terminal, and is thermally connected tothe thermal post and thereby thermally connected to the base; whereinthe adhesive is mounted on and extends above the base, covers andsurrounds the posts in the lateral directions and extends to peripheraledges of the assembly; wherein the pad extends above the adhesive; andwherein the thermal post extends into the first opening, the signal postextends into the second opening, the posts have the same thickness andare coplanar with one another and extend through the adhesive, the baseand the terminal have the same thickness and are coplanar with oneanother and extend below the adhesive, and tops and bottoms of the postsare coplanar with the adhesive.
 22. The assembly of claim 21, whereinthe semiconductor device is a semiconductor chip, is mounted on the heatspreader using a die attach, is electrically connected to the pad usinga wire bond and is thermally connected to the heat spreader using thedie attach.
 23. The assembly of claim 21, wherein the adhesive contactsthe posts, the base, the pad, the terminal and the routing line.
 24. Theassembly of claim 21, wherein the thermal post has a cut-off conicalshape in which its diameter decreases as it extends upwardly from thebase to its flat top which has a circular shape, and a cap is mounted onand above and adjacent to and covers in the upward direction and extendslaterally in the lateral directions from the top of the thermal post andhas a rectangular or square shape.
 25. The assembly of claim 24, whereinthe cap is coplanar with the pad above the adhesive.
 26. A semiconductorchip assembly, comprising: a semiconductor device; an adhesive thatincludes first and second openings; a heat spreader that includes athermal post and a base, wherein the thermal post is adjacent to thebase and extends above the base in an upward direction, and the baseextends below the thermal post in a downward direction opposite theupward direction and extends laterally from the thermal post in lateraldirections orthogonal to the upward and downward directions; a substratethat includes a pad and a dielectric layer, wherein first and secondapertures extend through the substrate; and a conductive trace thatincludes the pad, a terminal and a signal post, wherein the signal postextends below the pad and above the terminal and an electricallyconductive path between the pad and the terminal includes the signalpost; wherein the semiconductor device is above and overlaps the thermalpost, is electrically connected to the pad and thereby electricallyconnected to the terminal, and is thermally connected to the thermalpost and thereby thermally connected to the base; wherein the adhesiveis mounted on and extends above the base, extends into a first gap inthe first aperture between the thermal post and the substrate and into asecond gap in the second aperture between the signal post and thesubstrate, extends across the dielectric layer in the gaps, extendslaterally from the thermal post to or beyond the terminal and issandwiched between the thermal post and the dielectric layer, betweenthe signal post and the dielectric layer and between the base and thedielectric layer; wherein the substrate is mounted on the adhesive andextends above the base; wherein the pad extends above the dielectriclayer and the terminal extends below the adhesive; and wherein thethermal post extends into the first opening and the first aperture, thesignal post extends into the second opening and the second aperture, theposts have the same thickness and are coplanar with one another, and thebase and the terminal have the same thickness and are coplanar with oneanother.
 27. The assembly of claim 26, wherein the semiconductor deviceis an LED package that includes an LED chip.
 28. The assembly of claim27, wherein the LED package is electrically connected to the pad using afirst solder joint and is thermally connected to the heat spreader usinga second solder joint.
 29. The assembly of claim 26, wherein thesemiconductor device is a semiconductor chip.
 30. The assembly of claim29, wherein the chip is electrically connected to the pad using a wirebond and is thermally connected to the heat spreader using a die attach.31. The assembly of claim 26, wherein the adhesive contacts the thermalpost and the dielectric layer in the first gap, contacts the signal postand the dielectric layer in the second gap, and contacts the base, theterminal and the dielectric layer outside the gaps.
 32. The assembly ofclaim 26, wherein the adhesive covers and surrounds the posts in thelateral directions.
 33. The assembly of claim 26, wherein the adhesiveconformally coats sidewalls of the posts.
 34. The assembly of claim 26,wherein the adhesive is coplanar with tops and bottoms of the posts. 35.The assembly of claim 26, wherein the adhesive extends laterally fromthe thermal post beyond the terminal.
 36. The assembly of claim 26,wherein the adhesive extends to peripheral edges of the assembly. 37.The assembly of claim 26, wherein the thermal post is integral with thebase and the signal post is integral with the terminal.
 38. The assemblyof claim 26, wherein the thermal post has a cut-off conical shape inwhich its diameter decreases as it extends upwardly from the base to itsflat top, and the signal post has a cut-off conical shape in which itsdiameter decreases as it extends upwardly from the terminal to its flattop.
 39. The assembly of claim 26, wherein the base covers the thermalpost in the downward direction, supports the substrate and is spacedfrom peripheral edges of the assembly.
 40. The assembly of claim 26,wherein the conductive trace is spaced from the heat spreader, the padcontacts the dielectric layer, the terminal contacts the adhesive andthe signal post contacts the adhesive and the dielectric layer.
 41. Theassembly of claim 26, wherein the terminal is adjacent to and extendsbelow the signal post and extends laterally from the signal post in thelateral directions.
 42. The assembly of claim 26, wherein the heatspreader includes a cap that is above and adjacent to and covers in theupward direction and extends laterally in the lateral directions fromthe top of the thermal post.
 43. The assembly of claim 42, wherein thecap is coplanar with the pad above the dielectric layer.
 44. Theassembly of claim 42, wherein the cap has a rectangular or square shapeand the top of the thermal post has a circular shape.
 45. The assemblyof claim 42, wherein the cap is sized and shaped to accommodate athermal contact surface of the semiconductor device, and the top of thethermal post is not sized and shaped to accommodate the thermal contactsurface of the semiconductor device.
 46. A semiconductor chip assembly,comprising: a semiconductor device; an adhesive that includes first andsecond openings; a heat spreader that includes a thermal post, a baseand a cap, wherein the thermal post is adjacent to and integral with thebase, extends above the base in an upward direction and thermallyconnects the base and the cap, the base extends below the thermal postin a downward direction opposite the upward direction and extendslaterally from the thermal post in lateral directions orthogonal to theupward and downward directions, and the cap is above and adjacent to andcovers in the upward direction and extends laterally in the lateraldirections from a top of the thermal post; a substrate that includes apad, a routing line and a dielectric layer, wherein first and secondapertures extend through the substrate; a conductive trace that includesthe pad, the routing line, a terminal and a signal post, wherein therouting line is adjacent to pad, the signal post is adjacent to therouting line and the terminal, extends below the pad and the routingline and extends above the terminal, and an electrically conductive pathbetween the pad and the terminal includes the routing line and thesignal post; wherein the semiconductor device is mounted on the cap,overlaps the thermal post, does not overlap the signal post, iselectrically connected to the pad and thereby electrically connected tothe terminal, and is thermally connected to the cap and therebythermally connected to the base; wherein the adhesive is mounted on andextends above the base, extends into a first gap in the first aperturebetween the thermal post and the substrate and into a second gap in thesecond aperture between the signal post and the substrate, extendsacross the dielectric layer in the gaps, is sandwiched between thethermal post and the dielectric layer, between the signal post and thedielectric layer and between the base and the dielectric layer, coversand surrounds the posts in the lateral directions and extends toperipheral edges of the assembly; wherein the pad extends above thedielectric layer; and wherein the thermal post extends into the firstopening and the first aperture, the signal post extends into the secondopening and the second aperture, the posts have the same thickness andare coplanar with one another and extend through the adhesive and thedielectric layer, the base and the terminal have the same thickness andare coplanar with one another and extend below the adhesive and thedielectric layer, and tops and bottoms of the posts are coplanar withthe adhesive.
 47. The assembly of claim 46, wherein the semiconductordevice is a semiconductor chip, is mounted on the cap using a dieattach, is electrically connected to the pad using a wire bond and isthermally connected to the cap using the die attach.
 48. The assembly ofclaim 46, wherein the adhesive contacts the posts and the dielectriclayer in the gaps and contacts the base, the terminal and the dielectriclayer outside the gaps, and the dielectric layer contacts the pad andthe routing line and is spaced from the posts, the base and theterminal.
 49. The assembly of claim 46, wherein the thermal post has acut-off conical shape in which its diameter decreases as it extendsupwardly from the base to the cap, the signal post has a cut-off conicalshape in which its diameter decreases as it extends upwardly from theterminal to the routing line, the top of the thermal post has a circularshape and the cap has a rectangular or square shape.
 50. The assembly ofclaim 46, wherein the cap is coplanar with the pad above the dielectriclayer.